Aziridinium 3D Perovskites: Toward Semiconducting Films with Tunable Band Gaps

Abstract

Halide organic–inorganic perovskites are used as highly efficient semiconducting layers in photovoltaic and optoelectronic devices. However, the selection of known 3D organic–inorganic perovskites that have been processed into thin films is very limited. Here, we offer a route toward thin films of (AzrH)PbBr₃ and (AzrH)PbCl₃ (AzrH = aziridinium). The aziridinium perovskite films were deposited via a solution-based approach and make a contribution toward extension of the set of functional halide perovskite thin films. The developed procedure allows achieving thin films that keep the perovskite crystal structure up to 60 °C as confirmed by X-ray diffraction measurements. UV–vis absorption and photoluminescence measurements show that these bromide and chloride containing aziridinium perovskites form semiconducting thin films with optical band gaps of 2.40 and 3.20 eV and display emission at 545 and 407 nm, respectively. Interestingly, (AzrH)PbBr₃ thin films show an increased value of Stokes shift at room temperature (up to 80 meV) that makes this material promising for applications where reabsorption has to be avoided. UV and inverse photoelectron spectroscopies yield energy level positions that are in good agreement with calculations by density functional theory. This work uncovers the potential of aziridinium-based perovskite thin films regarding their semiconducting properties, thus widening the range of perovskites suitable for optoelectronic applications.