Exploring the Electrodeposition, the Termal Treatment, and the Photoelectrochemical Application of Non-Doped and Co-Doped Sb 2 Se 3 Thin Films

Among different kinds of materials used for photovoltaic (PV) applications, emerging thin film-based light absorbers with more common and less toxic elements are of increasing interest. In this scenario, Cu 2 ZnSn(Se,S) 4 is one of the most promising in terms of PV efficiency (certified 12.6%), 1,2 but the further improvements may be hindered by its chemical complexity. These considerations have led to a resurgent interest in earth-abundant less-complex non-toxic absorbers, such as Cu 3 P(S,Se) 4 , 3 CuSbS 2 , 5 and Sb 2 Se 3 . 6–8 Recently, several groups 6–8 have reported studies on Sb 2 Se 3 as an alternative material for PV device, highlighting its excellent properties; such as, its direct band gap in a range from 1.0 to 1.2 eV and high absorption coefficient >10 5 cm -1 at 1.2 eV. However, there are only few works of photoelectrochemical application, and about the effects of the thermal treatment and of the elemental doping on the properties of this semiconductor. In addition, in the most part of the papers, this material has been obtained by vacuum-based processes, which are often not desirable for the production of a low cost technology. Based on aforementioned perspectives, this work proposes the obtaining of Sb 2 Se 3 thin films by electrodeposition, a non-vacuum method, and shows an exploring study of the effects of the thermal treatment and of the addition of dopants. The main goal is to improve the optoelectronic quality and photoactivity toward hydrogen gas production of this material. Firstly, several Sb 2 Se 3 films were electrodeposited from SeO 2 and K(SbO)C 4 H 4 O 6 solutions at different concentrations, varying the supporting electrolytes, bath temperature, substrate, deposition potential and the total charge. Also, they were submitted to thermal treatment under Se atmosphere, at different temperatures and times. To evaluate the effects of each parameter on the morphological, structural and optoelectronic properties of the films, they were characterized by SEM, EDX, UV-vis spectroscopy, XRD and by photoelectrochemical measurements toward hydrogen gas evolution reaction, under simulated sun light (100 mW cm -2 ). The optimized condition of electro-obtaining of this material was achieved using the intensity of photocurrent of the films as guide. The optimized Sb 2 Se 3 film was obtained from a bath composed of 2.0 mM Se-source and 2.5 mM Sb-source in 0.5 M Na 2 SO 4 /H 2 SO 4 – pH 2, at 25 ºC and using a total charge of 600