Solar energy conversion properties and defect physics of ZnSiP$_2$

TL;DR

This paper introduces ZnSiP₂ as a stable, wide band gap, defect-tolerant material suitable for silicon-based photovoltaics, demonstrating a high open circuit voltage and promising defect physics for future optoelectronic applications.

Contribution

First demonstration of a ZnSiP₂ photovoltaic device showing high voltage and defect-tolerant properties suitable for integration with silicon.

Findings

ZnSiP₂ exhibits a high open circuit voltage of 1.3 V.

The material has a band gap of 2.1 eV and is defect-tolerant.

Intrinsic defects are shallow, with a minority carrier lifetime of 7 ns.

Abstract

Implementation of an optically active material on silicon has been a persistent technological challenge. For tandem photovoltaics using a Si bottom cell, as well as for other optoelectronic applications, there has been a longstanding need for optically active, wide band gap materials that can be integrated with Si. ZnSiP$_2$ is a stable, wide band gap (2.1 eV) material that is lattice matched with silicon and comprised of inexpensive elements. As we show in this paper, it is also a defect-tolerant material. Here, we report the first ZnSiP$_2$ photovoltaic device. We show that ZnSiP$_2$ has excellent photoresponse and high open circuit voltage of 1.3 V, as measured in a photoelectrochemical configuration. The high voltage and low band gap-voltage offset are on par with much more mature wide band gap III-V materials. Photoluminescence data combined with theoretical defect calculations illuminate the defect physics underlying this high voltage, showing that the intrinsic defects in ZnSiP$_2$ are shallow and the minority carrier lifetime is 7 ns. These favorable results encourage the development of ZnSiP$_2$ and related materials as photovoltaic absorber materials.