Amorphous-Silicon-Based Thin-Film Solar Cells Exhibiting Low Light-Induced Degradation

Abstract

We have applied a triode electrode configuration in the plasma-enhanced chemical vapor deposition (PECVD) process to grow intrinsic hydrogenated amorphous silicon (a-Si:H) light absorbers for the fabrication of p–i–n junction solar cells. Although the deposition rate is lower (0.1–0.3 Å/s) than that of the conventional diode PECVD process, the light-soaking stability of the solar cell is markedly improved and less sensitive to the cell thickness due to the reduced Si–H2 bond density in the a-Si:H i-layer. The a-Si:H single-junction solar cells exhibit low light-induced degradation of conversion efficiency (Δη/ηini∼10%) in comparison with that of high-efficiency solar cells reported to date. By applying the improved a-Si:H layers as top-cell absorbers in a-Si:H/hydrogenated microcrystalline silicon (µc-Si:H) tandem device, the light-induced degradation can be reduced even further (Δη/ηini\\lesssim5%). As a result, we obtain confirmed stabilized efficiencies of 9.6 and 11.3% for a-Si:H single-junction and a-Si:H/µc-Si:H tandem solar cells, respectively.