Effect of Light Induced Degradation on Passivating Properties of A-si:h Layers Deposited on Crystalline Si

Passivation properties of intrinsic hydrogenated amorphous silicon (i a-Si:H) layers on nand p-type doped monocrystalline silicon (c-Si) are studied in two thickness series. The effect of light soaking on the passivation performance of a-Si:H i-layers of varying thicknesses are evaluated. Within the thickness series, optimized i a-Si:H layers show very good passivation properties (Seff as low as 18 cm/s at an injection level of 10cm is achieved) for nas well as for p-type c-Si. Surprisingly these properties are not affected as expected by light soaking. The measured injection level dependence of the effective surface recombination velocity is modeled by considering recombination through amphoteric defects, characteristic of a-Si:H. Finally, heterojunction devices incorporating the thinnest passivation layer show maximum open circuit voltage (VOC) as high as 713mV. A best solar cell conversion efficiency of 17.6% with a VOC of 705mV is achieved on small area cell on flat n-type wafer. On p-type wafer, a VOC of 690mV and efficiency of 16.3% is achieved.