Band alignment of Sb2O3 and Sb2Se3

Huw Shiel,Tien-Lin Lee,Theodore D C Hobson,Matthew J Smiles,Jack E N Swallow,Oliver S Hutter,Thomas J Featherstone,Jonathan D Major,Laurie J Phillips,Pardeep K Thakur,Ken Durose,Tim D Veal,Leanne A H Jones

doi:10.1063/5.0055366

Abstract

Antimony selenide (Sb2Se3) possesses great potential in the field of photovoltaics (PV) due to its suitable properties for use as a solar absorber and good prospects for scalability. Previous studies have reported the growth of a native antimony oxide (Sb2O3) layer at the surface of Sb2Se3 thin films during deposition and exposure to air, which can affect the contact between Sb2Se3 and subsequent layers. In this study, photoemission techniques were utilized on both Sb2Se3 bulk crystals and thin films to investigate the band alignment between Sb2Se3 and the Sb2O3 layer. By subtracting the valence band spectrum of an in situ cleaved Sb2Se3 bulk crystal from that of the atmospherically contaminated bulk crystal, a valence band offset (VBO) of −1.72 eV is measured between Sb2Se3 and Sb2O3. This result is supported by a −1.90 eV VBO measured between Sb2O3 and Sb2Se3 thin films via the Kraut method. Both results indicate a straddling alignment that would oppose carrier extraction through the back contact of superstrate PV devices. This work yields greater insight into the band alignment of Sb2O3 at the surface of Sb2Se3 films, which is crucial for improving the performance of these PV devices.

Highlights

Sb2Se3 has attracted much attention in recent years for its potential as an absorber layer in photovoltaics (PV) and photocatalysis
The first method found the difference between the valence band spectra of a native oxide contaminated and an in situ cleaved bulk Sb2Se3 crystal, while the second utilized the Kraut method for a thermally evaporated Sb2O3 film on a polycrystalline Sb2Se3 grown by close space sublimation
A valence band offset (VBO) of À1:72 + 0:14 eV was measured via the valence band subtraction method between an Sb2Se3 crystal and the contaminant native Sb2O3 layer, leading to a straddling alignment

Summary

Introduction

Sb2Se3 has attracted much attention in recent years for its potential as an absorber layer in photovoltaics (PV) and photocatalysis. It has experienced a rapid rise in PV performance from 2% to nearly 10% in only a few years.. Sb and Se are Earth-abundant and low-cost, and Sb2Se3 can be fabricated via a wide variety of scalable methods.. Sb2Se3 attracts great interest due to its unusual 1D nanoribbon structure and Sb 5s2 lone pair of electrons.. Sb2Se3 attracts great interest due to its unusual 1D nanoribbon structure and Sb 5s2 lone pair of electrons.3,11,12 This structure means that strong, covalently bonded 1D nanoribbons are bound by weaker van der Waals interactions in two dimensions It has experienced a rapid rise in PV performance from 2% to nearly 10% in only a few years. The material has a very high absorption coefficient and a bandgap of 1.18 eV, making it a good candidate for use in PV. Sb and Se are Earth-abundant and low-cost, and Sb2Se3 can be fabricated via a wide variety of scalable methods. Sb2Se3 attracts great interest due to its unusual 1D nanoribbon structure and Sb 5s2 lone pair of electrons. This structure means that strong, covalently bonded 1D nanoribbons are bound by weaker van der Waals interactions in two dimensions

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