Aziridinium lead iodide: a stable, low bandgap hybrid halide perovskite for photovoltaics

TL;DR

This paper introduces aziridinium lead iodide, a new stable hybrid halide perovskite with a low bandgap suitable for photovoltaics, achieved through ab initio calculations emphasizing van der Waals interactions.

Contribution

It proposes a novel three-membered charged ring cation for hybrid perovskites, demonstrating improved stability and electronic properties via computational analysis.

Findings

Aziridinium lead iodide has a low ionization energy and suitable bandgap.

Van der Waals interactions are crucial for accurate polymorphism prediction.

The new perovskite shows enhanced stability compared to traditional ones.

Abstract

The low ionization energy of an $A$ site molecule is a very important factor, which determines the thermodynamical stability of $A$PbI$_3$ hybrid halide perovskites, while the size of the molecule governs the stable phase at room temperature and, eventually, the bandgap. It is challenging to achieve both a low ionization energy and the reasonable size for the PbI$_3$ cage to circumvent the stability issue inherent to hybrid halide perovskites. Here we propose a new three-membered charged ring radical, which demonstrates a low ionization energy that renders a good stability for its corresponding perovskite and a reasonable cation size that translates into a suitable bandgap for the photovoltaic application. We use ab initio calculations to evaluate a polymorphism of the crystal structure of the proposed halide hybrid perovskite, its stability and electronic properties in comparison to the mainstream perovskites, such as the methylammonium and formamidinium lead iodide. Our results highlight the importance of van der Waals interactions for predicting a correct polymorphism of the perovskite vs hexagonal crystal structure.