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

Here, we have synthesised a range of samples, with the formula (CH3NH3)1−2x(H3NC2H4NH3)xPbI3, with different levels of ethylenediammonium substitution to probe non-stoichiometry at the A-site of the perovskite. A single phase region was identified and is accompanied by a change in photophysical properties. The influence of aliovalent substitution with ethylenediammonium results in a decrease in HOMO level from −5.31 eV for x = 0 to −5.88 eV for x = 0.15.