Synthesis and characterization of hydrazine solution processed Cu12Sb4S13 film

Cu12Sb4S13 is a very potential non-toxic, earth-abundant absorber material for thin film solar cells yet its photovoltaic related properties are rarely explored so far. In this paper, we first developed a hydrazine solution process to fabricate phase-pure, highly crystalline, large grain Cu12Sb4S13 film and then carried out investigations to study the chemical, optical and electrical properties of Cu12Sb4S13 film in detail. Careful X-ray photoelectron spectroscopy (XPS) measurements indicated Cu12Sb4S13 could be oxidized into Cu3SbS4 in a sulfur rich atmosphere at elevated temperature, and the valance states of our Cu12Sb4S13 are determined as Cu+12Sb3+3Sb5+1S2−13 rather than the previously reported Cu+10Cu22+Sb3+4S2−13. Optical absorption investigation showed that Cu12Sb4S13 has a direct band gap of 1.47 eV. Ultraviolet photoelectron spectroscopy (UPS) study revealed that the conduction band and valence band are located at −3.52 eV and −4.99 eV relative to the vacuum level, respectively. Finally, we built a photodetector based on Cu12Sb4S13 film achieving 0.15 A/W responsivity and a heterojunction solar cell having 0.04% solar conversion efficiency. Our preliminary experimental study indicated that Cu12Sb4S13 may be a very attractive absorber material for photovoltaic application.