A new type of amorphous silicon solar cell with high thermal stability

A new type of solar cell has been developed with hydrogenated amorphous silicon (a-Si:H). The cell structure is glass/ITO/(P-a-Si:H)/(I-a-Si:H)/(SiO x -complexes)/(Al+O-complexes). In comparison with a conventional PIN-type a-Si solar cell glass/ITO/(P-a-Si:H)/(I-a-Si:H)/(N-a-Si:H)/Al, the new-type cell gives much higher stability against thermal degradation which is caused by internal diffusion of Si and Al at the interface of the back-side electrode on the solar cell. The conversion efficiency of the conventional cell decreased from 6% to less than 1%, but the new-type cell maintained the same efficiency of 5.2% (AM1, 100 mW/cm 2 ) after the storage at 120°C for 20 days. The new-type cell has the open circuit voltage V oc =0.86 (V), short-circuit current J sc =12 mA/cm 2 , and fill factor ff .=0.50, yielding conversion efficiency of η=5.2% under AM1.0 of 100 mW/cm 2 , and V oc =0.62 (V), J sc =18 µA/cm 2 , ff .=0.73 under a white fluorescent lamp of 200 lx. These photovoltaic parameters are almost the same as those of conventional PIN-type a-Si solar cells. In this paper, fabrication and photovoltaic performance of the thermal stability of the new-type cell are discussed in comparison with conventional solar cells.