Tilt-induced charge localisation in phosphide antiperovskite photovoltaics

TL;DR

This study investigates the structural stability and photovoltaic potential of antimonide phosphide antiperovskites, revealing a tilted orthorhombic phase that maintains high efficiency despite charge localisation effects.

Contribution

It identifies the true ground state structure of A3SbP antiperovskites and evaluates their photovoltaic efficiency and band alignment for solar cell applications.

Findings

Cubic structures are dynamically unstable.

Tilted orthorhombic phase is the ground state.

High photovoltaic efficiencies (24-31%) are achievable.

Abstract

Antiperovskites are a rich family of compounds with applications in battery cathodes, superconductors, solid-state lighting, and catalysis. Recently, a novel series of antimonide phosphide antiperovskites (A$_3$SbP, where A = Ca, Sr, Ba) were proposed as candidate photovoltaic absorbers due to their ideal band gaps, small effective masses and strong optical absorption. In this work, we explore this series of compounds in more detail using relativistic hybrid density functional theory. We reveal that the proposed cubic structures are dynamically unstable and instead identify a tilted orthorhombic Pnma phase as the ground state. Tilting is shown to induce charge localisation that widens the band gap and increases the effective masses. Despite this, we demonstrate that the predicted maximum photovoltaic efficiencies remain high (24-31% for 200 nm thin films) by bringing the band gaps into the ideal range for a solar absorber. Finally, we assess the band alignment of the series and suggest hole and electron contact materials for efficient photovoltaic devices.