Probing the structure-property-composition relationship in organic-inorganic tri-halide perovskites

Abstract

Since first being used in a solar cell, the efficiencies of organic-inorganic tri-halide perovskite solar cells have rapidly increased. Although one possible mechanism for the hysteresis exhibited by these solar cells is ionic migration, the creation of vacancies in organic-inorganic tri-halide perovskites remains unexplored experimentally. Here, we have synthesised a range of samples, with the formula (CH3NH3)1-2x(H3NC2H4NH3)xPbI3, with different levels of ethylenediammonium doping to probe non-stoichiometry at the A-site of the perovskite. A region of solid solution was identified and this results in a change in photophysical properties. The influence of doping with ethylenediammonium iodide results in a decrease in HOMO level from 5.31 eV for x = 0 to -5.88 eV for x = 0.15.