Publications
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M. Winter, D. Walter, D. Bredemeier, and J. Schmidt Light-induced lifetime degradation effects at elevated temperature in Czochralski-grown silicon beyond boron-oxygen-related degradation Journal Article Solar Energy Materials and Solar Cells 201 , 110060, (2019), ISSN: 0927-0248. Abstract | Links | BibTeX | Tags: boron-oxygen defect, Carrier lifetime, Czochralski-grown silicon, LeTID @article{Winter2019c,
title = {Light-induced lifetime degradation effects at elevated temperature in Czochralski-grown silicon beyond boron-oxygen-related degradation}, author = {M Winter and D Walter and D Bredemeier and J Schmidt}, doi = {10.1016/j.solmat.2019.110060}, issn = {0927-0248}, year = {2019}, date = {2019-10-01}, journal = {Solar Energy Materials and Solar Cells}, volume = {201}, pages = {110060}, abstract = {The effect of ‘Light and elevated Temperature Induced Degradation’ (LeTID) of the carrier lifetime is well known from multicrystalline silicon (mc-Si) wafers and solar cells. In this contribution, we perform a series of carrier lifetime measurements to examine, whether the same effect may also be observable in boron-doped Czochralski-grown silicon (Cz-Si). The Cz-Si samples of our study are illuminated (i) at room temperature, (ii) under standard regeneration conditions eliminating the boron-oxygen (BO) related defect (i.e. at 185 °C) and (iii) at a temperature of 80 °C, typical for the examination of the LeTID effect in mc-Si. We observe the typical decay of the carrier lifetime due to the activation of the BO-related defect. Beyond the BO degradation, applying standard solar cell processes, there is no indication for the activation of a second defect. On samples, whose surfaces are passivated by fired hydrogen-rich silicon nitride layers, an additional bulk lifetime degradation effect on a long timescale is observed in the Cz-Si material. However, defect generation rate and injection dependence of the lifetime suggest another defect type than the mc-Si-specific LeTID defect. We conclude that by applying processing steps that trigger LeTID in mc-Si, the same defect does not occur in the Cz-Si samples examined in this study. On a long timescale, however, a hitherto unknown type of defect is activated, which is different from the mc-Si-specific LeTID defect. A careful differentiation between the various kinds of recombination centres which may form during illumination at elevated temperatures is hence of utmost importance.}, keywords = {boron-oxygen defect, Carrier lifetime, Czochralski-grown silicon, LeTID}, pubstate = {published}, tppubtype = {article} } The effect of ‘Light and elevated Temperature Induced Degradation’ (LeTID) of the carrier lifetime is well known from multicrystalline silicon (mc-Si) wafers and solar cells. In this contribution, we perform a series of carrier lifetime measurements to examine, whether the same effect may also be observable in boron-doped Czochralski-grown silicon (Cz-Si). The Cz-Si samples of our study are illuminated (i) at room temperature, (ii) under standard regeneration conditions eliminating the boron-oxygen (BO) related defect (i.e. at 185 °C) and (iii) at a temperature of 80 °C, typical for the examination of the LeTID effect in mc-Si. We observe the typical decay of the carrier lifetime due to the activation of the BO-related defect. Beyond the BO degradation, applying standard solar cell processes, there is no indication for the activation of a second defect. On samples, whose surfaces are passivated by fired hydrogen-rich silicon nitride layers, an additional bulk lifetime degradation effect on a long timescale is observed in the Cz-Si material. However, defect generation rate and injection dependence of the lifetime suggest another defect type than the mc-Si-specific LeTID defect. We conclude that by applying processing steps that trigger LeTID in mc-Si, the same defect does not occur in the Cz-Si samples examined in this study. On a long timescale, however, a hitherto unknown type of defect is activated, which is different from the mc-Si-specific LeTID defect. A careful differentiation between the various kinds of recombination centres which may form during illumination at elevated temperatures is hence of utmost importance.
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D. C. Walter, D. Bredemeier, R. Falster, V. V. Voronkov, and J. Schmidt Easy-to-apply methodology to measure the hydrogen concentration in boron-doped crystalline silicon Journal Article Solar Energy Materials and Solar Cells 200 , 109970, (2019), ISSN: 0927-0248. Abstract | Links | BibTeX | Tags: Boron-hydrogen-pairs, crystalline silicon, Hydrogen @article{Walter2019c,
title = {Easy-to-apply methodology to measure the hydrogen concentration in boron-doped crystalline silicon}, author = {D C Walter and D Bredemeier and R Falster and V V Voronkov and J Schmidt}, doi = {10.1016/j.solmat.2019.109970}, issn = {0927-0248}, year = {2019}, date = {2019-09-15}, journal = {Solar Energy Materials and Solar Cells}, volume = {200}, pages = {109970}, abstract = {Hydrogen is a highly relevant impurity in crystalline silicon associated with a variety of effects particularly important in solar cell technology such as defect and surface passivation. It has been the subject of countless studies. Much of this however relies to a certain degree on speculation due to limitations in hydrogen measurement capability, making a direct quantitative correlation of these phenomena with the hydrogen content largely impossible so far. In this contribution, we apply recent advances in the understanding of hydrogen introduction and behaviour in silicon - in particular the conversion of quenched in dimeric hydrogen to boron hydrogen pairs (BH) - and introduce an easy-to-apply methodology to determine quantitatively the hydrogen concentration in bulk boron-doped silicon. The technique involves the measurement and analysis of changes to the bulk resistivity, as recorded by contactless eddy-current measurements, due to the formation of BH pairs during annealing at temperatures between 140 and 180 °C. To demonstrate the method, we apply it to boron-doped float-zone silicon wafers with SiNx:H coatings of different compositions, introducing different total hydrogen concentrations between 5 × 1014 and 1.3 × 1015 cm−3 into the silicon bulk during a fast-firing step. Without firing, the hydrogen content is below the detection limit of 3 × 1014 cm−3 for the 1 Ω cm test sample used.}, keywords = {Boron-hydrogen-pairs, crystalline silicon, Hydrogen}, pubstate = {published}, tppubtype = {article} } Hydrogen is a highly relevant impurity in crystalline silicon associated with a variety of effects particularly important in solar cell technology such as defect and surface passivation. It has been the subject of countless studies. Much of this however relies to a certain degree on speculation due to limitations in hydrogen measurement capability, making a direct quantitative correlation of these phenomena with the hydrogen content largely impossible so far. In this contribution, we apply recent advances in the understanding of hydrogen introduction and behaviour in silicon - in particular the conversion of quenched in dimeric hydrogen to boron hydrogen pairs (BH) - and introduce an easy-to-apply methodology to determine quantitatively the hydrogen concentration in bulk boron-doped silicon. The technique involves the measurement and analysis of changes to the bulk resistivity, as recorded by contactless eddy-current measurements, due to the formation of BH pairs during annealing at temperatures between 140 and 180 °C. To demonstrate the method, we apply it to boron-doped float-zone silicon wafers with SiNx:H coatings of different compositions, introducing different total hydrogen concentrations between 5 × 1014 and 1.3 × 1015 cm−3 into the silicon bulk during a fast-firing step. Without firing, the hydrogen content is below the detection limit of 3 × 1014 cm−3 for the 1 Ω cm test sample used.
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S. Schäfer, F. Haase, C. Hollemann, J. Hensen, J. Krügener, R. Brendel, and R. Peibst 26%-efficient and 2 cm narrow interdigitated back contact silicon solar cells with passivated slits on two edges Journal Article Solar Energy Materials and Solar Cells 200 , 110021, (2019), ISSN: 0927-0248. Abstract | Links | BibTeX | Tags: Back-contact solar cell, Edge loss, passivating contacts, perimeter recombination @article{Schäfer2019c,
title = {26%-efficient and 2 cm narrow interdigitated back contact silicon solar cells with passivated slits on two edges}, author = {S Schäfer and F Haase and C Hollemann and J Hensen and J Krügener and R Brendel and R Peibst}, doi = {10.1016/j.solmat.2019.110021}, issn = {0927-0248}, year = {2019}, date = {2019-09-15}, journal = {Solar Energy Materials and Solar Cells}, volume = {200}, pages = {110021}, abstract = {Perimeter recombination is a relevant loss mechanism, in particular for cells with a large perimeter-to-area ratio and with poorly passivated edges, e.g., cut or cleaved solar cells for shingled modules. We experimentally demonstrate that cut edges can be well passivated during front-end processing. The resulting cells have an efficiency of 26%. The designated cell area of our lab-type highly efficient cells is smaller than the total area of the wafer. This causes recombination losses in the masked perimeter region. We separate the active cell area from the wafer on two sides of the cell by slits to reduce the transport of carriers into the perimeter region. We apply a diffusion model to describe impact of the slits on the perimeter recombination. The slits have an effective surface recombination velocity of down to 9 cm/s, depending on the resistivity of the base. For a base resistivity of 80 Ωcm, the average cell efficiency increases by 0.7 %abs as compared to embedded cells and by 2.3 %abs as compared to laser-cut cells due to the passivated slits.}, keywords = {Back-contact solar cell, Edge loss, passivating contacts, perimeter recombination}, pubstate = {published}, tppubtype = {article} } Perimeter recombination is a relevant loss mechanism, in particular for cells with a large perimeter-to-area ratio and with poorly passivated edges, e.g., cut or cleaved solar cells for shingled modules. We experimentally demonstrate that cut edges can be well passivated during front-end processing. The resulting cells have an efficiency of 26%. The designated cell area of our lab-type highly efficient cells is smaller than the total area of the wafer. This causes recombination losses in the masked perimeter region. We separate the active cell area from the wafer on two sides of the cell by slits to reduce the transport of carriers into the perimeter region. We apply a diffusion model to describe impact of the slits on the perimeter recombination. The slits have an effective surface recombination velocity of down to 9 cm/s, depending on the resistivity of the base. For a base resistivity of 80 Ωcm, the average cell efficiency increases by 0.7 %abs as compared to embedded cells and by 2.3 %abs as compared to laser-cut cells due to the passivated slits.
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H. Schulte-Huxel, S. Blankemeyer, A. Morlier, R. Brendel, and M. Köntges Interconnect-shingling: Maximizing the active module area with conventional module processes Journal Article Solar Energy Materials and Solar Cells 200 , 109991, (2019), ISSN: 0927-0248. Abstract | Links | BibTeX | Tags: High efficiency PV modules, module integration, Shingled interconnection, Solar cell interconnection @article{Schulte-Huxel2019b,
title = {Interconnect-shingling: Maximizing the active module area with conventional module processes}, author = {H Schulte-Huxel and S Blankemeyer and A Morlier and R Brendel and M Köntges}, doi = {10.1016/j.solmat.2019.109991}, issn = {0927-0248}, year = {2019}, date = {2019-09-15}, journal = {Solar Energy Materials and Solar Cells}, volume = {200}, pages = {109991}, abstract = {We present a module fabrication process enabling gap-free interconnection of c-Si solar cells using solder-based interconnection technology with ribbons or wires. The interconnect-shingling process increases the module efficiency by avoiding the gaps between the solar cells. The process is applicable to bifacial cells and uses well-proven interconnection technologies. In contrast to previous adhesive-based shingled modules, the current transport is supported by interconnects, thus reducing the silver consumption for the cells’ metallization and avoiding cell overlap. We lay down the cells on structured encapsulant layers to reduce mechanical stress at the cell edges during lamination. Alternatively, the lamination process can be adapted to allow the encapsulant to reflow. This also results in a low pressure at sensitive cell parts. Both approaches avoid crack formation. We demonstrate the interconnect-shingling process with a proof-of-concept module having a aperture area efficiency of 22.1%. Applying 200 thermal cycles does not cause any crack formation.}, keywords = {High efficiency PV modules, module integration, Shingled interconnection, Solar cell interconnection}, pubstate = {published}, tppubtype = {article} } We present a module fabrication process enabling gap-free interconnection of c-Si solar cells using solder-based interconnection technology with ribbons or wires. The interconnect-shingling process increases the module efficiency by avoiding the gaps between the solar cells. The process is applicable to bifacial cells and uses well-proven interconnection technologies. In contrast to previous adhesive-based shingled modules, the current transport is supported by interconnects, thus reducing the silver consumption for the cells’ metallization and avoiding cell overlap. We lay down the cells on structured encapsulant layers to reduce mechanical stress at the cell edges during lamination. Alternatively, the lamination process can be adapted to allow the encapsulant to reflow. This also results in a low pressure at sensitive cell parts. Both approaches avoid crack formation. We demonstrate the interconnect-shingling process with a proof-of-concept module having a aperture area efficiency of 22.1%. Applying 200 thermal cycles does not cause any crack formation.
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S. Müller, F. Giovannetti, R. Reineke-Koch, O. Kastner, and B. Hafner Simulation study on the efficiency of thermochromic absorber coatings for solar thermal flat-plate collectors Journal Article Solar Energy 188 , 865 - 874, (2019), ISSN: 0038-092X. Abstract | Links | BibTeX | Tags: Flat-plate collector, Selective absorber coating, stagnation, system simulation, thermochromic @article{Müller2019c,
title = {Simulation study on the efficiency of thermochromic absorber coatings for solar thermal flat-plate collectors}, author = {S Müller and F Giovannetti and R Reineke-Koch and O Kastner and B Hafner}, doi = {10.1016/j.solener.2019.06.064}, issn = {0038-092X}, year = {2019}, date = {2019-08-01}, journal = {Solar Energy}, volume = {188}, pages = {865 - 874}, abstract = {We present a comparative simulative study to evaluate the efficiency and stagnation behavior of commercially available absorber coatings for solar thermal flat-plate collectors. A market survey has revealed different absorber coatings, which exhibit solar absorptances of α > 90% and thermal emittances ε of 5–90%. All these coatings can be classified as wet-chemically electroplated coatings on the basis of black chrome, highly selective sputtered PVD coatings, solar paints and novel thermochromic coatings. We calculated the annual solar collector energy output by means of collector simulations with the tool ScenoCalc and compared the collector efficiency of several absorber coatings. We have carried out TRNSYS simulations both with systems for solar domestic hot water preparation and solar-assisted space heating. In a solar domestic hot water system with a daily tapping volume of 100 L we report an increase in the auxiliary energy demand of up to 6% with black chrome, 7% with thermochromic and 21% with solar paint coatings compared to sputtered PVD coatings. In a solar combisystem the increase in the auxiliary energy demand does not exceed 1.4% for thermochromic and black chrome coatings and 6.1% for solar paints. The stagnation period can be reduced from 178 h per year (PVD coatings) to 118 h, 62 h and 11 h for black chrome, thermochromic and solar paint coatings, respectively. The maximum absorber temperatures decrease from 175 °C (PVD coatings) to 165 °C for black chrome, 145 °C for thermochromic and 135 °C for solar paint coatings.}, keywords = {Flat-plate collector, Selective absorber coating, stagnation, system simulation, thermochromic}, pubstate = {published}, tppubtype = {article} } We present a comparative simulative study to evaluate the efficiency and stagnation behavior of commercially available absorber coatings for solar thermal flat-plate collectors. A market survey has revealed different absorber coatings, which exhibit solar absorptances of α > 90% and thermal emittances ε of 5–90%. All these coatings can be classified as wet-chemically electroplated coatings on the basis of black chrome, highly selective sputtered PVD coatings, solar paints and novel thermochromic coatings. We calculated the annual solar collector energy output by means of collector simulations with the tool ScenoCalc and compared the collector efficiency of several absorber coatings. We have carried out TRNSYS simulations both with systems for solar domestic hot water preparation and solar-assisted space heating. In a solar domestic hot water system with a daily tapping volume of 100 L we report an increase in the auxiliary energy demand of up to 6% with black chrome, 7% with thermochromic and 21% with solar paint coatings compared to sputtered PVD coatings. In a solar combisystem the increase in the auxiliary energy demand does not exceed 1.4% for thermochromic and black chrome coatings and 6.1% for solar paints. The stagnation period can be reduced from 178 h per year (PVD coatings) to 118 h, 62 h and 11 h for black chrome, thermochromic and solar paint coatings, respectively. The maximum absorber temperatures decrease from 175 °C (PVD coatings) to 165 °C for black chrome, 145 °C for thermochromic and 135 °C for solar paint coatings.
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M. R. Vogt, R. Witteck, T. Gewohn, H. Schulte-Huxel, C. Schinke, K. Bothe, and R. Brendel Ray Tracing of Complete Solar Cell Modules Inproceedings OSA Advanced Photonics Congress (AP) 2019 (IPR, Networks, NOMA, SPPCom, PVLED), PW2C.1, Optical Society of America, (2019). Abstract | Links | BibTeX | Tags: Antireflection coatings, Geometric optics, Material properties, ray tracing, Reflection, Solar Cells @inproceedings{Vogt2019,
title = {Ray Tracing of Complete Solar Cell Modules}, author = {M R Vogt and R Witteck and T Gewohn and H Schulte-Huxel and C Schinke and K Bothe and R Brendel}, url = {http://www.osapublishing.org/abstract.cfm?URI=PVLED-2019-PW2C.1}, year = {2019}, date = {2019-07-29}, booktitle = {OSA Advanced Photonics Congress (AP) 2019 (IPR, Networks, NOMA, SPPCom, PVLED)}, journal = {OSA Advanced Photonics Congress (AP) 2019 (IPR, Networks, NOMA, SPPCom, PVLED)}, pages = {PW2C.1}, publisher = {Optical Society of America}, abstract = {We use the Daidalos-Cloud module ray tracer to quantify optical losses in a PERC+ cell module in three different spectrally resolved irradiance conditions. In mean annual irradiation conditions 8.6 mA/cm^2 are lost, in contrast to 7.6 mA/cm^2 in STC.}, keywords = {Antireflection coatings, Geometric optics, Material properties, ray tracing, Reflection, Solar Cells}, pubstate = {published}, tppubtype = {inproceedings} } We use the Daidalos-Cloud module ray tracer to quantify optical losses in a PERC+ cell module in three different spectrally resolved irradiance conditions. In mean annual irradiation conditions 8.6 mA/cm^2 are lost, in contrast to 7.6 mA/cm^2 in STC.
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M-U. Halbich, D. Zielke, R. Gogolin, R. Sauer-Stieglitz, W. Lövenich, and J. Schmidt Improved surface passivation and reduced parasitic absorption in PEDOT:PSS/c-Si heterojunction solar cells through the admixture of sorbitol Journal Article Scientific Reports 9 (1), 9775, (2019), ISSN: 2045-2322. Abstract | Links | BibTeX | Tags: PEDOT:PSS @article{Halbich2019,
title = {Improved surface passivation and reduced parasitic absorption in PEDOT:PSS/c-Si heterojunction solar cells through the admixture of sorbitol}, author = {M-U Halbich and D Zielke and R Gogolin and R Sauer-Stieglitz and W Lövenich and J Schmidt}, doi = {10.1038/s41598-019-46280-y}, issn = {2045-2322}, year = {2019}, date = {2019-07-05}, journal = {Scientific Reports}, volume = {9}, number = {1}, pages = {9775}, abstract = {We examine the impact of sorbitol admixture to the hole-conduction polymer PEDOT:PSS [poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate)] on the characteristics of PEDOT:PSS/crystalline silicon heterojunction solar cells. We fabricate solar cells where the PEDOT:PSS layer is deposited as a hole-collecting contact at the cell rear, whereas the electron-collecting front is conventionally processed by means of phosphorus diffusion. Surprisingly, we observe that the admixture of the infrared-transparent sorbitol not only improves the short-circuit density of the solar cells due to the reduction of the infrared parasitic absorption, but also improves the passivation quality of PEDOT:PSS on silicon and hence the open-circuit voltage of the solar cells. The series resistance is not influenced by the admixture of sorbitol up to 4.0 wt.% sorbitol admixture in the PEDOT:PSS dispersion, but shows a pronounced increase for larger sorbitol contents. The optimal sorbitol content concerning efficiency is hence 4.0 wt.%, leading to an energy conversion efficiency of 20.4% at one sun, which is more than 1% absolute higher compared to the efficiency of the reference cells without sorbitol.}, keywords = {PEDOT:PSS}, pubstate = {published}, tppubtype = {article} } We examine the impact of sorbitol admixture to the hole-conduction polymer PEDOT:PSS [poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate)] on the characteristics of PEDOT:PSS/crystalline silicon heterojunction solar cells. We fabricate solar cells where the PEDOT:PSS layer is deposited as a hole-collecting contact at the cell rear, whereas the electron-collecting front is conventionally processed by means of phosphorus diffusion. Surprisingly, we observe that the admixture of the infrared-transparent sorbitol not only improves the short-circuit density of the solar cells due to the reduction of the infrared parasitic absorption, but also improves the passivation quality of PEDOT:PSS on silicon and hence the open-circuit voltage of the solar cells. The series resistance is not influenced by the admixture of sorbitol up to 4.0 wt.% sorbitol admixture in the PEDOT:PSS dispersion, but shows a pronounced increase for larger sorbitol contents. The optimal sorbitol content concerning efficiency is hence 4.0 wt.%, leading to an energy conversion efficiency of 20.4% at one sun, which is more than 1% absolute higher compared to the efficiency of the reference cells without sorbitol.
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R. Witteck, P. Jäger, M. Rudolph, H. Mehlich, M. Köntges, T. Dullweber, R. Brendel, H. Schulte-Huxel, H-P. Sperlich, M. König, G. Köhler, and D. Landgraf UV-stable surface passivation for crystalline silicon cells in solar modules with UV light transmitting encapsulation materials Presentation Chicago, IL, USA, 20.06.2019, (46th IEEE Photovoltaic Specialist Conference (PVSC)). Abstract | BibTeX | Tags: UV-stable @misc{Witteck2019,
title = {UV-stable surface passivation for crystalline silicon cells in solar modules with UV light transmitting encapsulation materials}, author = {R Witteck and P Jäger and M Rudolph and H Mehlich and M Köntges and T Dullweber and R Brendel and H Schulte-Huxel and H-P Sperlich and M König and G Köhler and D Landgraf}, year = {2019}, date = {2019-06-20}, address = {Chicago, IL, USA}, abstract = {This contribution investigates the ultraviolet (UV) stability of dielectric passivation layers on n+-type industry-typical phosphorus diffused emitters having saturation current densities J0e in the range of 28 fA cm–2 to 75 fA cm–2. We prepare symmetrical silicon wafer test structures with various types of passivation layers and derive their saturation current densities from carrier life time measurements after exposure to various types of UV lamps. Our results reveal that UV illumination of samples with a typical industrial silicon nitride (SiNx) passivation layer increases the surface recombination. The illumination with narrow band lamps with intensity peak at 312 nm for a UV dose of 80 kWh m–2 significantly increases the J0e for these samples from 67 fA cm–2 to 287 fA cm–2. In contrast, a passivation layer stack consisting of a thermally grown silicon oxide and SiNx improves the UV stability of the samples. For this passivation layer stack, the J0e increases from a lower initial value of 36 fA cm–2 to only 41 fA cm–2. This finding allows for UV stable PERC cells in solar modules employing UV light transmitting encapsulation materials for an increased annual yield.}, note = {46th IEEE Photovoltaic Specialist Conference (PVSC)}, keywords = {UV-stable}, pubstate = {published}, tppubtype = {presentation} } This contribution investigates the ultraviolet (UV) stability of dielectric passivation layers on n+-type industry-typical phosphorus diffused emitters having saturation current densities J0e in the range of 28 fA cm–2 to 75 fA cm–2. We prepare symmetrical silicon wafer test structures with various types of passivation layers and derive their saturation current densities from carrier life time measurements after exposure to various types of UV lamps. Our results reveal that UV illumination of samples with a typical industrial silicon nitride (SiNx) passivation layer increases the surface recombination. The illumination with narrow band lamps with intensity peak at 312 nm for a UV dose of 80 kWh m–2 significantly increases the J0e for these samples from 67 fA cm–2 to 287 fA cm–2. In contrast, a passivation layer stack consisting of a thermally grown silicon oxide and SiNx improves the UV stability of the samples. For this passivation layer stack, the J0e increases from a lower initial value of 36 fA cm–2 to only 41 fA cm–2. This finding allows for UV stable PERC cells in solar modules employing UV light transmitting encapsulation materials for an increased annual yield.
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V. Titova, C. Flathmann, M. Seibt, and J. Schmidt Correlation of electronic and microscopic properties of TiOx/Al-based electron-selective contacts in silicon solar cells Presentation Chicago, IL, USA, 20.06.2019, (46th IEEE Photovoltaic Specialist Conference (PVSC)). Abstract | BibTeX | Tags: TiOx @misc{Titova2019,
title = {Correlation of electronic and microscopic properties of TiOx/Al-based electron-selective contacts in silicon solar cells}, author = {V Titova and C Flathmann and M Seibt and J Schmidt}, year = {2019}, date = {2019-06-20}, address = {Chicago, IL, USA}, abstract = {Contacts to crystalline silicon (c-Si) based on ultrathin layers of silicon oxide (SiOy) and titanium oxide (TiOx) have recently been shown to be highly selective to electrons if aluminum (Al) is used as top metal. Such SiOy/TiOx/Al electron-selective rear contacts result in an excellent passivation and a low contact resistance (and hence an excellent selectivity) after annealing at 350°C, whereas before annealing very high contact resistances are measured combined with a poor surface passivation. In this contribution, we examine the SiOy/TiOx/Al stack as implemented at the rear of our solar cells using Transmission Electron Microscopy (TEM)-based techniques and correlate electronic properties, deduced from measurements performed on solar cells, with the structural and compositional properties of the SiOy/TiOx/Al layer stack. We show that during annealing at 350°C, a significant interdiffusion mainly affecting the aluminum and to a lesser extend the oxygen and silicon distribution takes place within the layer stack, which seems to be the decisive prerequisite for the excellent electron conduction of the stack after annealing.}, note = {46th IEEE Photovoltaic Specialist Conference (PVSC)}, keywords = {TiOx}, pubstate = {published}, tppubtype = {presentation} } Contacts to crystalline silicon (c-Si) based on ultrathin layers of silicon oxide (SiOy) and titanium oxide (TiOx) have recently been shown to be highly selective to electrons if aluminum (Al) is used as top metal. Such SiOy/TiOx/Al electron-selective rear contacts result in an excellent passivation and a low contact resistance (and hence an excellent selectivity) after annealing at 350°C, whereas before annealing very high contact resistances are measured combined with a poor surface passivation. In this contribution, we examine the SiOy/TiOx/Al stack as implemented at the rear of our solar cells using Transmission Electron Microscopy (TEM)-based techniques and correlate electronic properties, deduced from measurements performed on solar cells, with the structural and compositional properties of the SiOy/TiOx/Al layer stack. We show that during annealing at 350°C, a significant interdiffusion mainly affecting the aluminum and to a lesser extend the oxygen and silicon distribution takes place within the layer stack, which seems to be the decisive prerequisite for the excellent electron conduction of the stack after annealing.
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F. Haase, C. Hollemann, S. Schaefer, J. Kruegener, R. Brendel, and R. Peibst Transferring the record p-type Si POLO-IBC cell technology towards an industrial level Presentation Chicago, IL, USA, 20.06.2019, (46th IEEE Photovoltaic Specialist Conference (PVSC)). Abstract | BibTeX | Tags: POLO @misc{Haase2019,
title = {Transferring the record p-type Si POLO-IBC cell technology towards an industrial level}, author = {F Haase and C Hollemann and S Schaefer and J Kruegener and R Brendel and R Peibst}, year = {2019}, date = {2019-06-20}, address = {Chicago, IL, USA}, abstract = {First, we evaluate the efficiency potential of our technology on p-type (B) Cz wafers using the lab-type process. We present a p-type Cz Si solar cell with an implied pseudo efficiency of 25.2 % measured before metallization. We had to reduce the thermal budget and to address the following implications: The two doped poly-Si on oxide (POLO) passivating contacts at the rear side are separated by a region of initially intrinsic (i) poly-Si. The latter is at least partially doped by lateral in-diffusion of dopants during junction formation. With increasing width of the (i) poly-Si region, the recombination at the p(i)n diode in the poly-Si decreases whereas the recombination at the (i) poly-Si/c-Si surface increases due to the bad passivation quality of the intrinsic poly-Si. As a second step, we suggest a process sequence for reducing the complexity down to that of a conventional PERC cell. This approach utilizes the Al‑BSF - a major strength of the existing p-PERC cells - and eliminates its weakness - that is the efficiency limiting emitter recombination at the front contacts - by using a POLO passivating contact. The process uses the same tools as a p-PERC cell and only adds one tool for poly-Si deposition. Our finite element simulations shows, that such a solar cell can reach an efficiency of 24.7 %}, note = {46th IEEE Photovoltaic Specialist Conference (PVSC)}, keywords = {POLO}, pubstate = {published}, tppubtype = {presentation} } First, we evaluate the efficiency potential of our technology on p-type (B) Cz wafers using the lab-type process. We present a p-type Cz Si solar cell with an implied pseudo efficiency of 25.2 % measured before metallization. We had to reduce the thermal budget and to address the following implications: The two doped poly-Si on oxide (POLO) passivating contacts at the rear side are separated by a region of initially intrinsic (i) poly-Si. The latter is at least partially doped by lateral in-diffusion of dopants during junction formation. With increasing width of the (i) poly-Si region, the recombination at the p(i)n diode in the poly-Si decreases whereas the recombination at the (i) poly-Si/c-Si surface increases due to the bad passivation quality of the intrinsic poly-Si. As a second step, we suggest a process sequence for reducing the complexity down to that of a conventional PERC cell. This approach utilizes the Al‑BSF - a major strength of the existing p-PERC cells - and eliminates its weakness - that is the efficiency limiting emitter recombination at the front contacts - by using a POLO passivating contact. The process uses the same tools as a p-PERC cell and only adds one tool for poly-Si deposition. Our finite element simulations shows, that such a solar cell can reach an efficiency of 24.7 %
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M. Rienäcker, E. L. Warren, T. F. Wietler, A. C. Tamboli, and R. Peibst Three-Terminal Bipolar Junction Bottom Cell as Simple as PERC: Towards Lean Tandem Cell Processing Presentation Chicago, IL, USA, 20.06.2019, (46th IEEE Photovoltaic Specialist Conference (PVSC)). Abstract | BibTeX | Tags: Tandem @misc{Rienäcker2019b,
title = {Three-Terminal Bipolar Junction Bottom Cell as Simple as PERC: Towards Lean Tandem Cell Processing}, author = {M Rienäcker and E L Warren and T F Wietler and A C Tamboli and R Peibst}, year = {2019}, date = {2019-06-20}, address = {Chicago, IL, USA}, abstract = {Silicon-based tandem cells can upgrade the dominating PERC technology and greatly increase the conversion efficiency. A novel approach, the three-terminal (3T) tandem using interdigitated back-contact (IBC) cells, was shown to combine the advantages of four- and two-terminal tandem cells at the expense of a more complex bottom cell fabrication process. In this paper, we propose a simplified and lean PERC-like 3T bipolar junction bottom cell featuring two minority carrier selective contacts and a single majority carrier selective contact, and thus resembling a bipolar junction transistor architecture. We present the lean PERC-like fabrication process and explain the working principle by using current-voltage measurements of illuminated 3T IBC cells.}, note = {46th IEEE Photovoltaic Specialist Conference (PVSC)}, keywords = {Tandem}, pubstate = {published}, tppubtype = {presentation} } Silicon-based tandem cells can upgrade the dominating PERC technology and greatly increase the conversion efficiency. A novel approach, the three-terminal (3T) tandem using interdigitated back-contact (IBC) cells, was shown to combine the advantages of four- and two-terminal tandem cells at the expense of a more complex bottom cell fabrication process. In this paper, we propose a simplified and lean PERC-like 3T bipolar junction bottom cell featuring two minority carrier selective contacts and a single majority carrier selective contact, and thus resembling a bipolar junction transistor architecture. We present the lean PERC-like fabrication process and explain the working principle by using current-voltage measurements of illuminated 3T IBC cells.
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J. Ulbikas, V. Ulbikaite, J. Denafas, R. Witteck, M. Köntges, M. Topič, F. Frontini, P. Bonomo, P. Macé, P. J. Bolt, A. Ulyashin, T. Haarberg, W. Palitzsch, B. Terheiden, I. Weiss, and A. Fuentes SUPER PV project – Developing innovative PV systems for cost reduction and enhanced performance Presentation Chicago, IL, USA, 18.06.2019, (46th IEEE Photovoltaic Specialist Conference (PVSC)). Abstract | BibTeX | Tags: Horizon 2020 @misc{Ulbikas2019,
title = {SUPER PV project – Developing innovative PV systems for cost reduction and enhanced performance}, author = {J Ulbikas and V Ulbikaite and J Denafas and R Witteck and M Köntges and M Topič and F Frontini and P Bonomo and P Macé and P J Bolt and A Ulyashin and T Haarberg and W Palitzsch and B Terheiden and I Weiss and A Fuentes}, year = {2019}, date = {2019-06-18}, address = {Chicago, IL, USA}, abstract = {PV deployment growth is an incomparable success story in the energy sector over recent years. Today PV has become one of the cheapest forms of electricity production globally and in some regions is now the most competitive unsubsidized form of electricity with emerging business models based purely on levelized cost of electricity (LCOE) estimations. Despite the positive cost and growth developments, due to competition from third countries European PV manufacturers are facing decline in production and without fast measures can completely disappear from the market. Europe PV landscape is today characterized by fragmentation of the value chain, while major solar actors are vertically integrated. This fragmentation is believed to be one of the major threats for the competitiveness of the European PV sector. SUPER PV is a collaborative European-funded project (within the framework of the Horizon 2020 Research and Innovation program) initiated in 2018 by 26 partners in reaction to this trend. In the SUPER PV project we are proposing a combined solution addressing both, technological improvements and data management methods based on utilization of Big Data Analytics, targeting a significant reduction of LCOE (26%-37%). This reduction will be achieved through demonstration of a careful selection of innovations, which will improve the main components of the LCOE. Introducing SUPERior quality PV systems will create conditions for accelerating large scale deployment of PV in Europe for both utility (non-urban) and residential (urban) scenarios and help EU PV businesses to regain leadership and competitiveness on world market.}, note = {46th IEEE Photovoltaic Specialist Conference (PVSC)}, keywords = {Horizon 2020}, pubstate = {published}, tppubtype = {presentation} } PV deployment growth is an incomparable success story in the energy sector over recent years. Today PV has become one of the cheapest forms of electricity production globally and in some regions is now the most competitive unsubsidized form of electricity with emerging business models based purely on levelized cost of electricity (LCOE) estimations. Despite the positive cost and growth developments, due to competition from third countries European PV manufacturers are facing decline in production and without fast measures can completely disappear from the market.
Europe PV landscape is today characterized by fragmentation of the value chain, while major solar actors are vertically integrated. This fragmentation is believed to be one of the major threats for the competitiveness of the European PV sector. SUPER PV is a collaborative European-funded project (within the framework of the Horizon 2020 Research and Innovation program) initiated in 2018 by 26 partners in reaction to this trend. In the SUPER PV project we are proposing a combined solution addressing both, technological improvements and data management methods based on utilization of Big Data Analytics, targeting a significant reduction of LCOE (26%-37%). This reduction will be achieved through demonstration of a careful selection of innovations, which will improve the main components of the LCOE. Introducing SUPERior quality PV systems will create conditions for accelerating large scale deployment of PV in Europe for both utility (non-urban) and residential (urban) scenarios and help EU PV businesses to regain leadership and competitiveness on world market. |
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S. Kajari-Schröder Contain the lead Journal Article Nature Energy (2019). Abstract | Links | BibTeX | Tags: perovskite @article{Kajari-Schröder2019,
title = {Contain the lead}, author = {S Kajari-Schröder}, doi = {10.1038/s41560-019-0414-2}, year = {2019}, date = {2019-06-17}, journal = {Nature Energy}, abstract = {Lead in perovskite solar cells is a potential environmental and health hazard if it is released from accidentally damaged panels. Now, the encapsulation of perovskite solar cells with self-healing polymers is shown to significantly reduce the risk of lead leakage from hail impact under a variety of weather conditions.}, keywords = {perovskite}, pubstate = {published}, tppubtype = {article} } Lead in perovskite solar cells is a potential environmental and health hazard if it is released from accidentally damaged panels. Now, the encapsulation of perovskite solar cells with self-healing polymers is shown to significantly reduce the risk of lead leakage from hail impact under a variety of weather conditions.
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J. Schmidt, D. Bredemeier, and D. C. Walter Fundamental Physics behind the Light-induced Degradation of Multicrystalline Silicon Solar Cells Presentation Chicago, IL, USA, 17.06.2019, (46th IEEE Photovoltaic Specialist Conference (PVSC)). @misc{Schmidt2019b,
title = {Fundamental Physics behind the Light-induced Degradation of Multicrystalline Silicon Solar Cells}, author = {J Schmidt and D Bredemeier and D C Walter}, year = {2019}, date = {2019-06-17}, address = {Chicago, IL, USA}, abstract = {State-of-the-art solar cells with passivated surfaces fabricated on multicrystalline silicon (mc-Si) wafers show a pronounced degradation in efficiency under illumination at elevated temperature, as it typically occurs during operation in a solar module. This effect, frequently denoted ‘LeTID’ (Light and elevated Temperature Induced Degradation), has been attributed to the activation of a bulk defect in mc-Si. We review recent studies aiming at understanding the defect physics behind this degradation effect, which is followed by a full regeneration. Experimental results of several labs indicate that hydrogen is directly involved in the responsible defect complex. We present our latest results showing for the first time a direct correlation of the extent of degradation with the hydrogen content in the silicon bulk. The second component of the defect seems to be a metal, with cobalt and nickel being the most likely candidates, as deduced from modeling the regeneration kinetics as a function of the wafer thickness. Several approaches of completely avoiding the instability in mc-Si solar cells are derived from the presented defect model, including (i) the tuning of the SiNx:H layers towards low-density films to minimize the in-diffusion of hydrogen into the wafer and (ii) the thinning of the mc-Si wafer, improving the getterability of the metal impurity component towards the surfaces.}, note = {46th IEEE Photovoltaic Specialist Conference (PVSC)}, keywords = {LID}, pubstate = {published}, tppubtype = {presentation} } State-of-the-art solar cells with passivated surfaces fabricated on multicrystalline silicon (mc-Si) wafers show a pronounced degradation in efficiency under illumination at elevated temperature, as it typically occurs during operation in a solar module. This effect, frequently denoted ‘LeTID’ (Light and elevated Temperature Induced Degradation), has been attributed to the activation of a bulk defect in mc-Si. We review recent studies aiming at understanding the defect physics behind this degradation effect, which is followed by a full regeneration. Experimental results of several labs indicate that hydrogen is directly involved in the responsible defect complex. We present our latest results showing for the first time a direct correlation of the extent of degradation with the hydrogen content in the silicon bulk. The second component of the defect seems to be a metal, with cobalt and nickel being the most likely candidates, as deduced from modeling the regeneration kinetics as a function of the wafer thickness. Several approaches of completely avoiding the instability in mc-Si solar cells are derived from the presented defect model, including (i) the tuning of the SiNx:H layers towards low-density films to minimize the in-diffusion of hydrogen into the wafer and (ii) the thinning of the mc-Si wafer, improving the getterability of the metal impurity component towards the surfaces.
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S. Müller, R. Reineke-Koch, F. Giovannetti, B. Hafner, and O. Kastner Feldversuch mit thermochromen Flachkollektoren in heizungsunterstützenden Solaranlagen Inproceedings Conexio. GmbH (Ed.): Tagungsunterlagen Symposium Solarthermie und innovative Wärmesysteme 2019, 172-187, Bad Staffelstein, Germany, (2019), ISBN: 978-3-948176-04-4. BibTeX | Tags: Flachkollektor @inproceedings{Müller2019,
title = {Feldversuch mit thermochromen Flachkollektoren in heizungsunterstützenden Solaranlagen}, author = {S Müller and R Reineke-Koch and F Giovannetti and B Hafner and O Kastner}, editor = {Conexio GmbH}, isbn = {978-3-948176-04-4}, year = {2019}, date = {2019-05-23}, booktitle = {Tagungsunterlagen Symposium Solarthermie und innovative Wärmesysteme 2019}, pages = {172-187}, address = {Bad Staffelstein, Germany}, keywords = {Flachkollektor}, pubstate = {published}, tppubtype = {inproceedings} } |
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E. Schneider, M. Littwin, M. Knoop, P. Pärisch, O. Kastner, and T. Ohrdes Entwicklung und messwertbasierte Parametrierung eines vereinfachten Gebäudemodells für die Quartiersmodellierung Inproceedings Conexio. GmbH (Ed.): Tagungsunterlagen Symposium Solarthermie und innovative Wärmesysteme 2019, 47-62, Bad Staffelstein, Germany, (2019), ISBN: 978-3-948176-04-4. BibTeX | Tags: Quartiersmodellierung @inproceedings{Schneider2019,
title = {Entwicklung und messwertbasierte Parametrierung eines vereinfachten Gebäudemodells für die Quartiersmodellierung}, author = {E Schneider and M Littwin and M Knoop and P Pärisch and O Kastner and T Ohrdes}, editor = {Conexio GmbH}, isbn = {978-3-948176-04-4}, year = {2019}, date = {2019-05-23}, booktitle = {Tagungsunterlagen Symposium Solarthermie und innovative Wärmesysteme 2019}, pages = {47-62}, address = {Bad Staffelstein, Germany}, keywords = {Quartiersmodellierung}, pubstate = {published}, tppubtype = {inproceedings} } |
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F. Weiland, M. Kirchner, V. Rensinghoff, F. Giovannetti, O. Kastner, D. Ridder, Y. Tekinbas, and H. Hachul Solarthermisch aktivierte Stahlsandwichelemente mit Mineralwollkern für den Industrie- und Gewerbebau Inproceedings Conexio. GmbH (Ed.): Tagungsunterlagen Symposium Solarthermie und innovative Wärmesysteme 2019, 223-238, Bad Staffelstein, Germany, (2019), ISBN: 978-3-948176-04-4. BibTeX | Tags: Solarthermie @inproceedings{Weiland2019,
title = {Solarthermisch aktivierte Stahlsandwichelemente mit Mineralwollkern für den Industrie- und Gewerbebau}, author = {F Weiland and M Kirchner and V Rensinghoff and F Giovannetti and O Kastner and D Ridder and Y Tekinbas and H Hachul}, editor = {Conexio GmbH}, isbn = {978-3-948176-04-4}, year = {2019}, date = {2019-05-23}, booktitle = {Tagungsunterlagen Symposium Solarthermie und innovative Wärmesysteme 2019}, pages = {223-238}, address = {Bad Staffelstein, Germany}, keywords = {Solarthermie}, pubstate = {published}, tppubtype = {inproceedings} } |
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C. Lampe, M. Kirchner, M. Littwin, F. Giovannetti, S. Asenbeck, and S. Fischer Experimentelle Untersuchungen an Testfeldern mit SOLINK-photovoltaisch-thermischen Kollektoren Inproceedings Conexio. GmbH (Ed.): Tagungsunterlagen Symposium Solarthermie und innovative Wärmesysteme 2019, 250-266, Bad Staffelstein, Germany, (2019), ISBN: 978-3-948176-04-4. @inproceedings{Lampe2019,
title = {Experimentelle Untersuchungen an Testfeldern mit SOLINK-photovoltaisch-thermischen Kollektoren}, author = {C Lampe and M Kirchner and M Littwin and F Giovannetti and S Asenbeck and S Fischer}, editor = {Conexio GmbH}, isbn = {978-3-948176-04-4}, year = {2019}, date = {2019-05-23}, booktitle = {Tagungsunterlagen Symposium Solarthermie und innovative Wärmesysteme 2019}, pages = {250-266}, address = {Bad Staffelstein, Germany}, keywords = {PVT}, pubstate = {published}, tppubtype = {inproceedings} } |
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S. Fischer, S. Bachmann, B. Schiebler, F. Giovannetti, and M. Köhl 40 % Reduktion des solaren Wärmepreises durch die Kombination unterschiedlicher Optimierungsmaßnahmen Inproceedings Conexio. GmbH (Ed.): Tagungsunterlagen Symposium Solarthermie und innovative Wärmesysteme 2019, 327-338, Bad Staffelstein, Germany, (2019), ISBN: 978-3-948176-04-4. BibTeX | Tags: solarer Wärmepreis @inproceedings{Fischer2019,
title = {40 % Reduktion des solaren Wärmepreises durch die Kombination unterschiedlicher Optimierungsmaßnahmen}, author = {S Fischer and S Bachmann and B Schiebler and F Giovannetti and M Köhl}, editor = {Conexio GmbH}, isbn = {978-3-948176-04-4}, year = {2019}, date = {2019-05-23}, booktitle = {Tagungsunterlagen Symposium Solarthermie und innovative Wärmesysteme 2019}, pages = {327-338}, address = {Bad Staffelstein, Germany}, keywords = {solarer Wärmepreis}, pubstate = {published}, tppubtype = {inproceedings} } |
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T. Ohrdes Wind-Solar-Wärmepumpen-Quartier (EnEff:Stadt Verbundvorhaben) Presentation Berlin, Germany, 21.05.2019, (Berliner ENERGIETAGE 2019). BibTeX | Tags: Wärmepumpe @misc{Ohrdes2019,
title = {Wind-Solar-Wärmepumpen-Quartier (EnEff:Stadt Verbundvorhaben)}, author = {T Ohrdes}, year = {2019}, date = {2019-05-21}, address = {Berlin, Germany}, note = {Berliner ENERGIETAGE 2019}, keywords = {Wärmepumpe}, pubstate = {published}, tppubtype = {presentation} } |
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M. Rienäcker, E. L. Warren, M. Schnabel, H. Schulte-Huxel, R. Niepelt, R. Brendel, P. Stradins, A. C. Tamboli, and R. Peibst Back-contacted bottom cells with three terminals: Maximizing power extraction from current-mismatched tandem cells Journal Article Progress in Photovoltaics: Research and Applications 27 (5), 410-423, (2019). Abstract | Links | BibTeX | Tags: 3T, bipolar junction transistor tandem, bottom cell, current-mismatch, interdigitated back contact cell (IBC), tandem solar cell, three terminal @article{Rienäcker2019,
title = {Back-contacted bottom cells with three terminals: Maximizing power extraction from current-mismatched tandem cells}, author = {M Rienäcker and E L Warren and M Schnabel and H Schulte-Huxel and R Niepelt and R Brendel and P Stradins and A C Tamboli and R Peibst}, doi = {10.1002/pip.3107}, year = {2019}, date = {2019-05-01}, journal = {Progress in Photovoltaics: Research and Applications}, volume = {27}, number = {5}, pages = {410-423}, abstract = {Abstract Multi-junction cells can significantly improve the energy yield of photovoltaic systems over a single-junction cell. The internal interconnection scheme of the subcells is an important aspect in determining the resulting levelized cost of electricity. For a dual-junction cell, two approaches are commonly discussed: series-connected tandem cells with two terminals or independently working subcells in a four-terminal (4T) tandem device. In this paper, we explore the working principle and the operation modes of a third, rarely discussed option: a three-terminal (3T) tandem cell using a back-contacted bottom cell with 3Ts. We use current–voltage measurements of illuminated 3T interdigitated back contact cells and confirm that the front and rear base contacts are at similar quasi-Fermi level positions, which enables the bottom cell to either efficiently collect surplus carriers, in the case of a current-limiting or carrier injecting top cell, or inject majority carriers, in the case of a current-limiting bottom cell. As a result, no current matching is needed. The power output of an idealized 3T bottom cell without resistive effects is independent of the current density applied from the top cell. These characteristics of the 3T bottom cells enable a 3T tandem to operate as efficiently as a 4T tandem, while being compatible with monolithic design and not requiring intermediate grids. We propose a simple equivalent circuit model including additional resistive effects, which describes a real 3T bottom cell and achieves excellent agreement to the experiment. We deduce design guidelines for a 3T bottom cell in different operation regimes.}, keywords = {3T, bipolar junction transistor tandem, bottom cell, current-mismatch, interdigitated back contact cell (IBC), tandem solar cell, three terminal}, pubstate = {published}, tppubtype = {article} } Abstract Multi-junction cells can significantly improve the energy yield of photovoltaic systems over a single-junction cell. The internal interconnection scheme of the subcells is an important aspect in determining the resulting levelized cost of electricity. For a dual-junction cell, two approaches are commonly discussed: series-connected tandem cells with two terminals or independently working subcells in a four-terminal (4T) tandem device. In this paper, we explore the working principle and the operation modes of a third, rarely discussed option: a three-terminal (3T) tandem cell using a back-contacted bottom cell with 3Ts. We use current–voltage measurements of illuminated 3T interdigitated back contact cells and confirm that the front and rear base contacts are at similar quasi-Fermi level positions, which enables the bottom cell to either efficiently collect surplus carriers, in the case of a current-limiting or carrier injecting top cell, or inject majority carriers, in the case of a current-limiting bottom cell. As a result, no current matching is needed. The power output of an idealized 3T bottom cell without resistive effects is independent of the current density applied from the top cell. These characteristics of the 3T bottom cells enable a 3T tandem to operate as efficiently as a 4T tandem, while being compatible with monolithic design and not requiring intermediate grids. We propose a simple equivalent circuit model including additional resistive effects, which describes a real 3T bottom cell and achieves excellent agreement to the experiment. We deduce design guidelines for a 3T bottom cell in different operation regimes.
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D. Bredemeier, D. C. Walter, R. Heller, and J. Schmidt Impact of Hydrogen-Rich Silicon Nitride Material Properties on Light-Induced Lifetime Degradation in Multicrystalline Silicon Journal Article Forthcoming physica status solidi (RRL) – Rapid Research Letters 1900201, Forthcoming. Abstract | Links | BibTeX | Tags: Carrier lifetime, Hydrogen, LeTID defects, light-induced lifetime degradation, silicon nitride, ulticrystalline silicon @article{Bredemeier2019b,
title = {Impact of Hydrogen-Rich Silicon Nitride Material Properties on Light-Induced Lifetime Degradation in Multicrystalline Silicon}, author = {D Bredemeier and D C Walter and R Heller and J Schmidt}, doi = {10.1002/pssr.201900201}, year = {2019}, date = {2019-04-29}, journal = {physica status solidi (RRL) – Rapid Research Letters}, pages = {1900201}, abstract = {The root cause of “Light and Elevated Temperature Induced Degradation” (LeTID) of the carrier lifetime in multicrystalline silicon (mc-Si) wafers is investigated by depositing hydrogen-rich silicon nitride (SiNx:H) films of different compositions on boron-doped mc-Si wafers. The extent of LeTID observed in mc-Si after rapid thermal annealing (RTA) shows a positive correlation with the amount of hydrogen introduced from the SiNx:H layers into the bulk. The concentration of in-diffused hydrogen is quantified via measuring the resistivity change due to the formation of boron–hydrogen pairs in boron-doped float-zone silicon wafers processed in parallel to the mc-Si wafers. The measurements clearly show that the in-diffusion of hydrogen into the silicon bulk during RTA depends on both the atomic density of the SiNx:H film as well as the film thickness. Importantly, the impact of SiNx:H film properties on LeTID shows the same qualitative dependence as the hydrogen content in the silicon bulk, providing evidence that hydrogen is involved in the LeTID defect activation process.}, keywords = {Carrier lifetime, Hydrogen, LeTID defects, light-induced lifetime degradation, silicon nitride, ulticrystalline silicon}, pubstate = {forthcoming}, tppubtype = {article} } The root cause of “Light and Elevated Temperature Induced Degradation” (LeTID) of the carrier lifetime in multicrystalline silicon (mc-Si) wafers is investigated by depositing hydrogen-rich silicon nitride (SiNx:H) films of different compositions on boron-doped mc-Si wafers. The extent of LeTID observed in mc-Si after rapid thermal annealing (RTA) shows a positive correlation with the amount of hydrogen introduced from the SiNx:H layers into the bulk. The concentration of in-diffused hydrogen is quantified via measuring the resistivity change due to the formation of boron–hydrogen pairs in boron-doped float-zone silicon wafers processed in parallel to the mc-Si wafers. The measurements clearly show that the in-diffusion of hydrogen into the silicon bulk during RTA depends on both the atomic density of the SiNx:H film as well as the film thickness. Importantly, the impact of SiNx:H film properties on LeTID shows the same qualitative dependence as the hydrogen content in the silicon bulk, providing evidence that hydrogen is involved in the LeTID defect activation process.
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K. T. VanSant, J. Simon, J. F. Geisz, E. L. Warren, K. L. Schulte, A. J. Ptak, M. S. Young, M. Rienäcker, H. Schulte-Huxel, R. Peibst, and A. C. Tamboli Toward Low-Cost 4-Terminal GaAs//Si Tandem Solar Cells Journal Article ACS Applied Energy Materials 2 (4), 2375–2380, (2019). Abstract | Links | BibTeX | Tags: Tandem @article{VanSant2019,
title = {Toward Low-Cost 4-Terminal GaAs//Si Tandem Solar Cells}, author = {K T VanSant and J Simon and J F Geisz and E L Warren and K L Schulte and A J Ptak and M S Young and M Rienäcker and H Schulte-Huxel and R Peibst and A C Tamboli}, doi = {10.1021/acsaem.9b00018}, year = {2019}, date = {2019-04-22}, journal = {ACS Applied Energy Materials}, volume = {2}, number = {4}, pages = {2375–2380}, abstract = {Mechanically stacked III–V-on-Si (III–V//Si) tandem solar cells have demonstrated efficiencies beyond what can theoretically be achieved by single junction Si solar cells, but III–V costs are currently at least an order of magnitude higher than Si costs. Recent techno-economic analysis shows that costs could be substantially reduced by replacing traditional metalorganic vapor phase epitaxy (MOVPE) with a lower-cost III–V deposition technique, such as hydride vapor phase epitaxy (HVPE). This study analyzes the performance of an HVPE-grown GaAs top cell incorporated into a 4-terminal (4T) GaAs//Si tandem cell that achieved an efficiency of 29%, which is the highest solar cell efficiency fabricated without expensive deposition techniques such as MOVPE or MBE. We compare these results to an MOVPE-grown GaAs//Si tandem cell that has the same structure. Finally, we model optimizations to the HVPE-grown GaAs top cell and provide a near-term pathway to 31.4% efficiency with a low-cost III–V deposition technique.}, keywords = {Tandem}, pubstate = {published}, tppubtype = {article} } Mechanically stacked III–V-on-Si (III–V//Si) tandem solar cells have demonstrated efficiencies beyond what can theoretically be achieved by single junction Si solar cells, but III–V costs are currently at least an order of magnitude higher than Si costs. Recent techno-economic analysis shows that costs could be substantially reduced by replacing traditional metalorganic vapor phase epitaxy (MOVPE) with a lower-cost III–V deposition technique, such as hydride vapor phase epitaxy (HVPE). This study analyzes the performance of an HVPE-grown GaAs top cell incorporated into a 4-terminal (4T) GaAs//Si tandem cell that achieved an efficiency of 29%, which is the highest solar cell efficiency fabricated without expensive deposition techniques such as MOVPE or MBE. We compare these results to an MOVPE-grown GaAs//Si tandem cell that has the same structure. Finally, we model optimizations to the HVPE-grown GaAs top cell and provide a near-term pathway to 31.4% efficiency with a low-cost III–V deposition technique.
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J. Schmidt Surface Passivation of Crystalline Silicon Solar Cells: Past, Present and Future Presentation Leuven, Belgium, 10.04.2019, (SiliconPV 2019, 9th International Conference on Silicon Photovoltaics). BibTeX | Tags: surface passivation @misc{Schmidt2019,
title = {Surface Passivation of Crystalline Silicon Solar Cells: Past, Present and Future}, author = {J Schmidt}, year = {2019}, date = {2019-04-10}, address = {Leuven, Belgium}, note = {SiliconPV 2019, 9th International Conference on Silicon Photovoltaics}, keywords = {surface passivation}, pubstate = {published}, tppubtype = {presentation} } |
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L. Helmich, D. C. Walter, and J. Schmidt Direct Examination of the Boron-Oxygen Deactivation Via Electroluminescence Characterization of Cz-Si Solar Cells Under Regeneration Conditions Presentation Leuven, Belgium, 10.04.2019, (SiliconPV 2019, 9th International Conference on Silicon Photovoltaics). BibTeX | Tags: boron-oxygen @misc{Helmich2019,
title = {Direct Examination of the Boron-Oxygen Deactivation Via Electroluminescence Characterization of Cz-Si Solar Cells Under Regeneration Conditions}, author = {L Helmich and D C Walter and J Schmidt}, year = {2019}, date = {2019-04-10}, address = {Leuven, Belgium}, note = {SiliconPV 2019, 9th International Conference on Silicon Photovoltaics}, keywords = {boron-oxygen}, pubstate = {published}, tppubtype = {presentation} } |