Effect of Interfacial Energetics on Charge Transfer from Lead Halide Perovskite to Organic Hole Conductors

The control and optimization of interfacial charge transfer processes is crucial to the design of efficient perovskite solar cells. Herein, we measure the yield and kinetics of hole transfer across the methylammonium lead triiodide perovskite|polymeric hole transport material heterojunction, as a function of the interfacial energy offset, ∆E between the highest occupied molecular orbital of the hole transport material and the valence band of the perovskite. A combination of steady-state and time-resolved photoluminescence, along with transient absorption spectroscopy revealed that only a small driving energy (∆E~0.07eV) is required to induce highly efficient hole transfer. The findings of this paper suggest that further improvements in the open-circuit voltage, and so the power conversion efficiency, of perovskite solar cells could be achieved by incorporating hole transport materials that provide an interfacial energy offset in the range 0 < ∆E < 0.18eV