A Liquid Junction Photoelectrochemical Solar Cell Based on p-Type MeNH₃PbI₃ Perovskite with 1.05 v Open-Circuit Photovoltage

A liquid junction photoelectrochemical (PEC) solar cell based on p-type methylammonium lead iodide (p-MeNH₃PbI₃) perovskite with a large open-circuit voltage is developed. MeNH₃PbI₃ perovskite is readily soluble or decomposed in many common solvents. However, the solvent dichloromethane (CH₂Cl₂) can be employed to form stable liquid junctions. These were characterized with photoelectrochemical cells with several redox couples, including I₃^-/I^-, Fc/Fc⁺, DMFc/DMFc⁺, and BQ/BQ^. (where Fc is ferrocene, DMFc is decamethylferrocene, BQ is benzoquinone) in CH₂Cl₂. The solution-processed MeNH₃PbI₃ shows cathodic photocurrents and hence p-type behavior. The difference between the photocurrent onset potential and the standard potential for BQ/BQ^. is 1.25 V, which is especially large for a semiconductor with a band gap of 1.55 eV. A PEC photovoltaic cell, with a configuration of p-MeNH₃PbI₃/CH₂Cl₂, BQ (2 mM), BQ^. (2 mM)/carbon, shows an open-circuit photovoltage of 1.05 V and a short-circuit current density of 7.8 mA/cm² under 100 mW/cm² irradiation. The overall optical-to-electrical energy conversion efficiency is 6.1%. The PEC solar cell shows good stability for 5 h under irradiation.