Surface Recombination and Collection Efficiency in Perovskite Solar Cells from Impedance Analysis

The large diffusion lengths recurrently measured in perovskite single crystals and films signal small bulk nonradiative recombination flux and locate the dominant carrier recombination processes at the outer interfaces. Surface recombination largely determines the photovoltaic performance, governing reductions under short-circuit current and open-circuit voltage. Quantification of recombination losses is necessary to reach full understanding of the solar cell operating principles. Complete impedance model is given, which connects capacitive and resistive processes to the electronic kinetics at the interfaces. Carrier collection losses affecting the photocurrent have been determined to equal 1%. Photovoltage loss is linked to the decrease in surface hole density, producing 0.3 V reduction with respect to the ideal radiative limit. Our approach enables a comparison among different structures, morphologies, and processing strategies of passivation and buffer layers.