Metal-halide perovskite solar cells rival the best inorganic solar cells in power conversion efficiency, providing the outlook for efficient, cheap devices. In order for the technology to mature and approach the ideal Shockley-Queissier efficiency, experimental tools are needed to diagnose what processes limit performances, beyond simply measuring electrical characteristics often affected by parasitic effects and difficult to interpret. Here we study the microscopic origin of recombination currents causing photoconversion losses with an all-optical technique, measuring the electron-hole free energy as a function of the exciting light intensity. Our method allows assessing the ideality factor and breaks down the electron-hole recombination current into bulk defect and interface contributions, providing an estimate of the limit photoconversion efficiency, without any real charge current flowing through the device. We identify Shockley-Read-Hall recombination as the main decay process in insulated perovskite layers and quantify the additional performance degradation due to interface recombination in heterojunctions.

Charge generation and transport in (CH₃NH₃)PbI_3−xCl_x sensitized mesostructured solar cells are investigated. A highly efficient charge generation is directly proven by time correlated single photon counting analysis. Photoinduced absorption and transient photovoltage investigations depict double charge recombination dynamics. To explain the high device performances according to those spectroscopic observations, we suggest the existence of two complementary paths for electron transport, involving either TiO₂ or perovskite matrixes.