Influence of the asymmetrical defect state distribution at the a-Si:H/cSi interface on the performance of homo-heterojunction solar cells

摘要

An emerging cell concept called HH (homo-heterojunction) solar cells possesses a potential to realize high photoelectric conversion efficiency, which has been investigated by the aid of numerical simulation tool AFORS-HET recently. Taking into account the fact that the distribution of defect states (acceptor N-itA and donor N-itD) defect states) at the hetero-interface does not have strictly symmetrical shape, we present a simulation study of a ZnO/(p)a-Si:H/(p)cSi/(n)cSi/(i)a-Si:H/(n)a-Si:H/Ag solar cell with particular emphasis on the role of the asymmetrical defect state distribution (N-itA/N-itD = 1) at the front (p)a-Si:H/(p)cSi interface. The presented results suggest that the HH structure has a better tolerance of the broken symmetry of defect state distribution at the hetero-interface, which benefits from inherent favourable band alignment of HH structure. An in-depth understanding of transport properties can help to improve the efficiency of a silicon-based solar cell, and provide useful guidance for design strategies of photovoltaic devices.