Spectral Downshifting and Passivation Effects Using 2D Perovskite (OAm)₂SnBr₄ Films to Enhance the Properties of Si Nanowire Solar Cells

Si nanowires (Si NWs) are emerging as a promising candidate for photovoltaics due to their significant light-trapping characteristics. However, Si NWs have a high density of surface traps, which lead to carrier recombination; also, thermalization due to the absorption of high-energy photons causes the dissipation of input solar energy. In this study, Ag/Ti/n+/p-Si NWs/MoOx/Ag solar cells were formed based on Si NWs with MoOx as a hole transport layer. A highly luminescent 2D perovskite (C18H35NH3)2SnBr4 was applied to the front surface of the cell. This 2D perovskite with oleylamine (OAm) spacer passivates the surface of the Si NWs. In addition to the passivation effect, the 2D perovskite (OAm)2SnBr4 causes a downshifting and energy-transfer effect, which reduces the heat loss and raises the conversion efficiency. This effect has often been observed in semiconductor quantum dots and is also evident in 2D perovskite films, resulting in improved Jsc, Voc, and fill factor and an increase in the overall cell efficiency to 18%