Defect properties of Sb2Se3 thin film solar cells and bulk crystals

Abstract

As an absorber in photovoltaic devices, Sb2Se3 has rapidly achieved impressive power conversion efficiencies despite the lack of fundamental knowledge about its electronic defects. Here, we present a deep level transient spectroscopy (DLTS) study of deep level defects in both bulk crystal and thin film device material. DLTS study of Bridgman-grown n-type bulk crystals revealed traps at 358, 447, 505, and 685 meV below the conduction band edge. Of these, the energetically close pair at 447 and 505 meV could only be resolved using the isothermal transient spectroscopy (rate window variation) method. A completed Sb2Se3 thin film solar cell displayed similar trap spectra with traps identified at 378, 460, and 690 meV. The comparable nature of defects in thin film and bulk crystal material implies that there is minimal impact of polycrystallinity in Sb2Se3 supporting the concept of benign grain boundaries.