Competition of Carrier Separation and Recombination for an Optimized Electrode Configuration for Flexible Thin-Film Solar Cells.

Abstract

The inhibition of the rapid recombination of photochemical charges at heterointerfaces and the promotion of transfer and extraction are central to photoelectric conversion in solar cells. With the use of Cu4Bi4S9 nanoribbons-graphene sheets (CBS-GSs) as a hybrid photosensitive layer and the growth of ZnO nanowires on Zn2SnO4 nanowires (ZTO-ZnO) for the electron transfer layer, a flexible solar cell ZTO-ZnO/CBS-GSs was prepared on a stainless steel mesh. In this study, time-resolved fluorescence spectroscopy (TFS) and transient surface photovoltage (TPV) were used to describe the transition and transport process for the photogenerated carriers. With a high fill factor (0.76) and improved electron mobility for the ZTO-ZnO nanostructure, a high photoelectric conversion efficiency of 11.6% was obtained, which was evidently higher than that of a ZTO/CBS-GSs cell (9.2%) and a ZnO nanoparticles/CBS-GSs cell (3.9%). The efficient dissociation of photogenerated carriers at CBS-GSs interfaces, rapid transfer of free electrons in the ZTO-ZnO system, and fast extraction of holes from the selective NiO layer with an optimized architecture led to a superior performance. The charge recombination at the interface can be determined by electrochemical impedance spectroscopy (EIS). Active exploration via inevitable competition between charge separation and recombination (TFS, TPV, EIS, etc.) can provide insights into the entire dynamic process and a separation mechanism for photoinduced carriers, which can also promote the application of flexible thin-film solar cells.