Large area nanocrystalline silicon based multi-junction solar cells with superior light soaking stability

We present our progress in attaining high efficiency nc-Si:H solar cells at high deposition rates with superior light soaking stability. We have focused our effort on three areas: (i) improving the spatial uniformity and homogeneous properties for nc-Si:H, such as crystallite grain size and volume fraction, (ii) optimizing nucleation and seed layer during the initial growth of the nc-Si:H film, and (iii) optimizing nc-Si:H bulk growth and grain evolution. We have conducted an extensive study of the effect of process parameters including hydrogen dilution profiling, VHF power, and substrate temperature on the nc-Si:H film properties and component cell characteristics. We also conducted light soaking tests both indoors and outdoors. The a-Si:H/nc-Si:H/nc-Si:H triple-junction cells incorporating the optimized nc-Si:H component cells show significantly higher performance, achieving an 11.2% AM1.5 stabilized efficiency for both encapsulated large-area (464 cm2) cells and inter-connected modules (2320 cm2). To the best of our knowledge, this is the highest stabilized efficiency for a large-area thin-film silicon module.