Thin-film polycrystalline silicon solar cells on ceramic substrates with a V_(oc) above 500 mV

摘要

Thin-film polycrystalline-silicon solar cells offer a promising alternative to standard silicon solar cells. Until now, however, obtained efficiencies are too low to lead to a cost reduction in photovoltaics. To obtain cells with higher efficiencies, polycrystalline-silicon layers need large grains, good passivation and an optimized cell design. In this work we compare pc-Si solar cells with an amorphous silicon-crystalline silicon heterojunction emitter to cells with a diffused phosphorus emitter. In heterojunction cells, hydrogen passivation was carried out before emitter formation, which appears to make it more effective. Open-circuit voltages (V_(oc)) were much higher for cells with a heterojunction emitter, reaching values up to 520 mV. A maximum efficiency of 5.3% was obtained on the heterojunction cells, while the homojunction cells led to substantially lower efficiencies. A cell concept based on a heterojunction emitter seems therefore most favorable to lead to highly efficient thin-film pc-Si solar cells. The high V_(oc) and efficiency values obtained in this work form an important step towards cost-effective polycrystalline-silicon solar cells.