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

Hydrogenated amorphous silicon (a-Si:H) films are prepared by plasma-enhanced chemical vapor deposition (PECVD) with a triode electrode configuration in which a SiH4-H-2 glow-discharge plasma is confined spatially away from the substrate. Although the deposition rate (0.1-0.5 angstrom/s) is lower than that of the conventional diode PECVD process (2.5 angstrom/s), the light-induced degradation in conversion efficiency (triangle eta/eta(ini)) of a single-junction solar cell is substantially reduced (e.g., triangle eta/eta(ini) similar to 10% at an absorber thickness of t(i)=250nm), and efficiencies after light soaking (LS) maintain >9% for t(i)=180-390nm. By applying the improved a-Si:H layers as top cell absorbers in a-Si:H/hydrogenated microcrystalline silicon (mu c-Si:H) tandem solar cells, the light-induced degradation can be reduced further (e.g., triangle eta/eta(ini) similar to 5% at t(i)=250nm). As a result, we obtain confirmed stabilized efficiencies of 9.6% (LS condition: 100mW/cm(2), 50 degrees C, 1000h) and 11.9% (LS condition: 125mW/cm(2), 48 degrees C, 310h) for a-Si:H single-junction and a-Si:H/mu c-Si:H tandem solar cells, respectively. Copyright (c) 2012 John Wiley & Sons, Ltd.