POPEI – Production technologies for high-performance cost-effective IBC solar cells

The ISFH sub-project of the POPEI project aims to develop an industrially producible, extremely cost-effective process for the production of IBC (Interdigitated Back Contact) solar cells based on gallium (Ga) doped silicon wafers, local plasma-enhanced chemical vapor deposition (PECVD) deposition of selective poly-Si contacts as well as novel cleaning processes. For this purpose, ISFH is developing a very short process sequence using direct local PECVD-SiO2/n-poly-silicon (Si) deposition through shadow masks. In case of success, this can save a complex patterning of the poly-Si e.g. by diffusion / oxidation, oxide ablation and potassium hydroxide (KOH) etching, making the IBC process much more cost effective and in the optimum case even shorter than the PERC+ (Passivated Emitter and Rear Cell) industrial process.

If the ISFH sub-project is successful, IBC cells will be producible for the first time with lower manufacturing costs than today’s mainstream PERC+ solar cells. At the same time, the IBC2 concept replaces the efficiency-limiting phosphorus emitter of the PERC+ cell with n-poly-Si contacts, which, in combination with HCl/O3 cleaning (hydrochloric acid/ozone), increases the efficiency potential of the cell to over 25% according to simulations. Due to the very short POPEI project duration of two years, the first objective is to prove the feasibility of the IBC2. ISFH is creating new layouts for glass shadow masks, which will be manufactured by LPKF and subsequently evaluated at ISFH and Centrotherm for the use of local PECVD-poly-Si deposition for IBC solar cells. In addition, ISFH is developing new HCl/O3-based cleaning processes together with RENA.