A-SIO:H thin films with increased light induced degradation stability for thin film silicon solar cells

Silicon based multi-junction thin film solar cells suffer from light-induced degradation (LID) due to the Staebler-Wronski effect. The top-absorber in such a cell is usually made out of intrinsic amorphous silicon (i)a-Si:H which suffers most from LID. Intrinsic amorphous silicon oxide (i)a-SiO:H promises an increased LID stability. We deposited (i)a-SiO:H absorber layers with different ratios of CO2/SiH4 by radio frequency plasma enhanced chemical vapour deposition (RF-PECVD). The (i)a-SiO:H absorber layers were characterized regarding to their electrical and optical properties. The defect density Nd has been determined by the constant photocurrent method (CPM). It was found that (i)a-SiO:H has an increased LID stability compared to a-Si:H. The measurement results were then transferred into the simulation software Advanced Semiconductor Analysis (ASA). We carried out simulations for the initial and light soaked state of solar cells with a reference (i)a-Si:H absorber layer and the new (i)a-SiO:H absorber layer. The cells showed after light soaking nearly equal efficiency.