Tunable optoelectronic properties of radio frequency sputter-deposited Sb2Se3 thin films: Role of growth angle and thickness

Abstract

In thin film photovoltaics, antimony selenide (Sb2Se3) is making a mark as an important absorber layer for its attractive structural, optical, and electrical properties. Several deposition techniques are used to grow Sb2Se3 films, albeit growth angle-dependent physical properties of Sb2Se3 films are yet to be explored in a systematic manner. In this work, we investigate the roles of growth angle (in the range of 0°-87°) and thickness (250 and 1000 nm) in governing optoelectronic properties of Sb2Se3 films grown by radio frequency sputter deposition technique. It is interesting to note that upon increasing the growth angle, a systematic enhancement in the optical band-gap takes place. This is accompanied by a systematic reduction in the work function of these amorphous films with increasing growth angle. Subsequently, after postgrowth annealing at 573 K for 180 s (in vacuum) all Sb2Se3 films undergo a structural phase transition from amorphous to crystalline one. Following this, the band-gap and work function of these films also get modified. This study paves the way to fabricate Sb2Se3 films having tunable optoelectronic properties like absorption coefficient, band-gap, and work function. Thus, it should be extremely useful to select Sb2Se3 films having optimal thickness and optoelectronic properties to fabricate Sb2Se3 absorber layer-based multi-junction hole-blocking solar cells having improved cell efficiencies.