Enhanced light-trapping for micromorph tandem solar cells by LP-CVD ZnO

Abstract

Amorphous silicon p-i-n single-junction and "micromorph" (amorphous/microcrystalline) tandem solar cells have been deposited on "inhouse" LP-CVD zinc oxide front-TCO. ZnO shows superior light-trapping behavior compared to SnO/sub 2/ (Asahi type U). Up-scaling to modules by laser scribing has been developed, both for amorphous single-junction and for micromorph tandem cells on LP-CVD ZnO. Within our laboratory-size reactor an amorphous mini-module (22 cm/sup 2/) with an aperture efficiency of 8.4% after 200 h of light-soaking could be fabricated. In case of micromorph tandem modules (24 cm/sup 2/) a stabilized aperture area efficiency of 9.8% (initial 11%) has been achieved. Modified micromorph tandem cells with an intermediate reflector between the a-Si:H top and the pc-Si:H bottom cell show almost stable behavior with respect to light-soaking.