Bessel-Beam Direct Write of the Etch Mask in a Nano-Film of Alumina for High-Efficiency Si Solar Cells

article

2024

authors
Katkus, Tomas and Ng, Soon Hock and Mu, Haoran and Le An, Nguyen Hoai and Stonyt\.e, Dominyka and Khajehsaeidimahabadi, Zahra and Seniutinas, Gediminas and Baltrukonis, Justas and Ul\vcinas, Orestas and Mikutis, Mindaugas and Sabonis, Vytautas and Nishijima, Yoshiaki and Rienäcker, Michael and Römer, Udo and Krügener, Jan and Peibst, Robby and John, Sajeev and Juodkazis, Saulius

journal
Advanced Engineering Materials

doi:10.1002/adem.202400711

abstract

Large surface area applications such as high efficiency \textgreater26% solar cells require surface patterning with 1--10 \textgreekmm periodic patterns at high fidelity over 1--10 cm21 - \left(textcmright)$^2$ areas (before up scaling to 1 m2 \left(textmright)$^2$) to perform at, or exceed, the Lambertian (ray optics) limit of light trapping. Herein, a pathway is shown to high-resolution sub-1 \textgreekmm etch mask patterning by ablation using direct femtosecond laser writing performed at room conditions (without the need for a vacuum-based lithography approach). A Bessel beam is used to alleviate the required high surface tracking tolerance for ablation of 0.3--0.8 \textgreekmm diameter holes in 40 nm alumina Al2O3\left(textAlright)$_2$ \left(textOright)$_3$--mask at high writing speed, 7.5 cm s$-$1; a patterning rate 1 cm2 per 20 min. Plasma etching protocol was optimized for a zero-mesa formation of photonic-crystal-trapping structures and smooth surfaces at the nanoscale level. The maximum of minority carrier recombination time of 2.9 ms was achieved after the standard wafer passivation etch; resistivity of the wafer was 3.5 \textgreekW cm. Scaling up in area and throughput of the demonstrated approach is outlined.