Perovskite-based photovoltaics have been rapidly developed, with record power conversion efficiencies now exceeding 22%. In order to rationally design efficient and stable perovskite solar cells, it is important to understand not only charge trapping and recombination events, but also processes occurring at the perovskite/transport material (TM) interface, such as charge transfer and interfacial recombination. In this work, time-resolved microwave conductivity measurements are performed to investigate these interfacial processes for methylammonium lead iodide and various state-of-the-art organic TMs. A global kinetic model is developed, which accurately describes both the dynamics of excess charges in the perovskite layer and transfer to charge-specific TMs. The authors conclude that for state-of-the-art materials, such as Spiro-OMeTAD and PCBM, the charge extraction efficiency is not significantly affected by intra-band gap traps for trap densities under 10¹⁵ cm^–3. Finally, the transfer rates to C60, PCBM, EDOT-OMeTPA, and Spiro-OMeTAD are sufficient to outcompete second order recombination under excitation densities representative for illumination by AM1.5.

This paper studies photochemical upconversion in solutions of octaethyl porphyrin (OEP) and diphenyl anthracene (DPA). The system has been widely used as a standard model system in the field of photochemical upconversion. Although, the kinetics of elementary processes contributing to photochemical upconversion in it have been extensively studied, there has been no research on the efficiency of upconversion in the system, despite of the fact that this parameter is detrimental for potential applications of photochemical upconversion process. We determine the yield of photochemical upconversion in a number of metal based OEP/DPA systems. Additionally, we studied the dependence of kinetic, and efficiency parameters of the process on the core metal of the porphyrin. We showed that the overall efficiency of photochemical upconversion depends significantly on the core metal of the triplet sensitizer porphyrin molecule. We attribute this effect to the differences in efficiency of triplet energy transfer from metal based OEP to DPA depending on the core metal.