Study on the correlation between the photovoltaic effect and the defect density at the surface of a poly-Si solar cell by using photoconductive atomic force microscopy (PC-AFM)

Abstract

In this study, we designed and fabricated a poly-Si-based solar cell device by using conventional Si processes. The electrical properties, such as the open-circuit voltage (Voc), the short-circuit current (Isc), the fill factor, the external quantum efficiency (EQE) and the efficiency of prepared solar cell devices, were characterized with a standardized measurement system. Also, the correlation between the photoinduced current and the variation of the defect density was then investigated for various locations by using a photoconductive atomic force microscopy (PC-AFM) system. We verified that in a high-defect-density region such as a grain boundary, a triple junction or a crack, photoinduced carriers easily recombined and induced a decrease in the diffusion length and a low level of photoinduced current. Moreover, we suggest a very effective method to reduce the contact resistance between the cantilever tip and the sample surface, which can disturb the flow of photoinduced current.