Cyclopropenium (C₃H₃)⁺ as an Aromatic Alternative A‑Site Cation for Hybrid Halide Perovskite Architectures

Hybrid halide perovskites are an emerging class of photovoltaic materials, boasting high solar efficiencies from relatively simple preparations. However, the chemical diversity of the A-site organic cation is limited, generally due to steric constraints of the (PbI3)− cage. Herein we describe the use of a non-benzenoid Hückel aromatic, (C3H3)+, as a viable alternative to the readily employed methylammonium, formamidinium, and guanidinium A-site cations. (C3H3)+ may lead to greater moisture stability due to the lack of an acidic proton relative to the current (H–NR3)+-based systems while still boasting a narrow electronic band gap (Eg = 1.5 eV) and mobile holes and electrons (mh* = −1.27 and me* = 0.77, respectively).