Effect of the organic cation on the optical properties of Lead Iodine perovskites

TL;DR

This study investigates how 14 different organic cations influence the optical properties of lead iodine perovskites using first-principles calculations, revealing key contributions to absorption and potential pathways to reduce toxicity.

Contribution

It provides a detailed analysis of the impact of various organic cations on perovskite optical properties and introduces a method to identify substitutions that lower toxicity while preserving absorption.

Findings

Pb-Pb intra-species transitions dominate near the bandgap.

Absorption properties are similar across different cations.

Splitting absorption coefficients helps identify less toxic element substitutions.

Abstract

The effect of 14 organic cations on the optical properties of the lead iodine perovskite is analyzed. The electronic and optical properties are obtained using first principles. The absorption coefficients are split into inter-atomic species components in order to quantify all of the contributions. For energies close to the bandgaps, the main contribution is from the Pb-Pb intra-species transitions. For higher energy this contribution is still important in addition to I-I and Pb-I contributions, and to the 3 and 4 species term. Almost all absorption properties are qualitatively similar. Furthermore, this absorption coefficient splitting also allows the optical characteristics that the substitution of Pb by another element should satisfy to be identified in order to reduce the toxicity because of Pb while maintaining a high absorption capacity.