Angermann, H.; Conrad, E.; Korte, L.; Rappich, J.; Schulze, T.F.; Schmidt, M.: Passivation of textured substrates for a-Si:H/c-Si hetero-junction solar cells: Effect of wet-chemical smoothing and intrinsic a-Si:H interlayer. Materials Science and Engineering B 159-160 (2009), p. 219-223
10.1016/j.mseb.2008.10.044
Abstract:
Abstract The effect of both wet-chemical smoothing and deposition of intrinsic a-Si:H buffer layer on elec-tronic surface and interface properties was investigated for monocrystalline p-type silicon substrates with pyramidal light trapping structures. For the complete removal of native and wet-chemical ox-ides during the final etching in HF (1%), the treatment time was optimized for each etching step, which leads to a significantly reduced density of rechargeable states on the substrate surface. This density of substrate surface states could be preserved during subsequent deposition of intrinsic and doped a Si:H buffer layers on the front and back sides by plasma enhanced chemical vapour deposi-tion (PECVD). Solar cells prepared with optimized wet-chemical wafer treatment improved signifi-cantly in fill factor. The application of intrinsic buffer layers results an additional improvement of the open circuit voltage by ~50 mV, leading to efficiencies enhanced by ~3% (absolute value) for ZnO/(n,i)a-Si:H/(p)c-Si/(i,p+)a Si:H/Al cells, as compared to cells with non-optimized substrate treatment and without (i)a-Si:H buffer layers.