Growth and Properties of Sb-Ge-Se Thin Films: A Promising Material for Sustainable Photovoltaic Devices Development

Abstract

Sb-Ge chalcogenides are known as effective phase change materials, making them ideal for optical data storage applications, detectors, and sensors. However, there have been no photovoltaic devices developed using these materials to date. In this work, Sb-Ge-Se crystalline thin films with different [Sb]/[Ge] atomic ratios are successfully grown for the first time through the selenization of co-evaporated Sb and Ge layers. The impact of the Se addition and temperature during the selenization process on the composition, structural, morphological, vibrational, and optical properties of the Sb-Ge-Se layers is investigated. The coexistence of Sb2Se3 and GeSe2 has been confirmed using various characterization techniques, including Grazing Incidence X-ray diffraction, Fourier Transform Infrared Spectroscopy, X-ray Photoelectron Spectroscopy and Raman spectroscopy. Additionally, Scanning Transmission Electron Microscopy has revealed Ge-enrichment regions surrounding the Sb2Se3 crystals. The composition of the co-evaporated film and final Ge content in the chalcogenide film govern the band gap energy, increasing from 1.41 to 1.83 eV. We present the inaugural operational SLG/Mo/Sb-Ge-Se/CdS/ZnO/ITO photovoltaic devices with a total efficiency of 1.34%. The primary factors limiting the device performance are the significant CdS diffusion into the active layer and the high defect density, as determined by Capacitance-Voltage and Drive-Level Capacitance Profiling. The devices exhibit excellent stability after 1 year of storage in ambient air. These first prototypes of Sb-Ge-Se crystalline thin films pave the way for advancement in the development of sustainable and stable photovoltaic devices.