Rate limiting interfacial hole transfer in Sb 2 S 3 solid-state solar cells

Transfer of photogenerated holes from the absorber species to the p-type hole conductor is fundamental to the performance of solid-state sensitized solar cells. In this study, we comprehensively investigate hole diffusion in the Sb 2 S 3 absorber and hole transfer across the Sb 2 S 3 –CuSCN interface in the TiO 2 –Sb 2 S 3 –CuSCN system using femtosecond transient absorption spectroscopy, carrier diffusion modeling, and photovoltaic performance studies. Transfer of photogenerated holes from Sb 2 S 3 to CuSCN is found to be dependent on Sb 2 S 3 film thickness, a trend attributed to diffusion in the Sb 2 S 3 absorber. However, modeling reveals that this process is not adequately described by diffusion limitations alone as has been assumed in similar systems. Therefore, both diffusion and transfer across the Sb 2 S 3 –CuSCN interface are taken into account to describe the hole transfer dynamics. Modeling of diffusion and interfacial hole transfer effects reveal that interfacial hole transfer, not diffusion, is the predominant factor dictating the magnitude of the hole transfer rate, especially in thin (