High-efficiency thin-film silicon solar cells with improved light-soaking stability

摘要

Hydrogenated amorphous silicon (a-Si: H) films are prepared by plasma-enhanced chemical vapor deposition (PECVD) with a triode electrode configuration in which a SiH_4-H_2 glow-discharge plasma is confined spatially away from the substrate. Although the deposition rate (0.1-0.5 A/s) is lower than that of the conventional diode PECVD process (2.5 A/s), the light-induced degradation in conversion efficiency (/_(ini)) of a single-junction solar cell is substantially reduced (e.g., /_(ini) 10% at an absorber thickness of t_i = 250 nm), and efficiencies after light soaking (LS) maintain >9% for t_i = 180-390 nm. By applying the improved a-Si: H layers as top cell absorbers in a-Si: H/hydrogenated microcrystalline silicon (c-Si: H) tandem solar cells, the light-induced degradation can be reduced further (e.g., /_(ini) 5% at t_i = 250 nm). As a result, we obtain confirmed stabilized efficiencies of 9.6% (LS condition: 100mW/cm~2, 50 , 1000 h) and 11.9% (LS condition: 125 mW/cm~2, 48, 310 h) for a-Si:H single-junction and a-Si:H/c-Si:H tandem solar cells, respectively.