Sb₂(S,Se)₃, is a relevant semiconductor free of critical raw materials that is receiving an increasing interest for photovoltaic (PV) applications, demonstrating solar cells in superstrate configuration with a record efficiency of 6.5%. The semiconductor is characterised by a 1D crystalline formation which in principle favours formation of benign grain boundaries and anisotropic conduction properties. Additionally Sb₂Se₃ has a high degree of flexibility in terms of substrate type, due to its relatively low synthesis temperature (300-400 ºC). This allows the use of different substrates as polymers, steels, ceramics and TCO/glass. The compound has also the possibility to tune the band gap between 1.1 and 1.9 eV, which opens very interesting perspectives for wide band gap solar cells suitable for energy harvesting in indoor applications, semi-transparent devices or high efficiency tandem devices. This high versatility make this compound very promising for ubiquitous applications based on the integration of PV devices in products and systems requiring light weight, mechanical flexibility and/or optical transparency. 

This work reports a systematic study of Sb₂Se₃ layers and substrate configuration solar cells that were fabricated using a reactive annealing treatment of Sb evaporated precursors. The study analyses the dependence of the physico-chemical properties of the layers and the optoelectronic characteristics of the devices on the pressure and temperature used during the Se reactive annealing process, as well as on the characteristics of the substrate layers, having used different kinds of substrates including both transparent (FTO) and non-transparent (Mo, Al, Au, Ag, W) back contact materials. The results obtained have allowed us to achieve  reproducible functional devices using near atmospheric pressure at 320ºC on Mo coated soda lime glass substrate with a promising efficiency of 5.6% close to the 6.5% certified world record.

This study involved a deep characterization of the fundamental properties of the synthesised layers that that have been correlated with the optoelectronic characterization of the devices. The results allow us to observe the formation of continuous layers with large and homogeneous crystals, reporting for the first time a weak PL close to 1.3eV in agreement with the band gap value obtained by IQE. Finally, the systematic vibrational characterization of the layers performed under resonant and non- resonant Raman conditions –including measurements on reference single crystal Sb2Se3 – has allowed the identification of 15 Raman peaks of the compound.