Sb2S3 thin films by ultrasonic spray pyrolysis of antimony ethyl xanthate

Synthesis of antimony chalcogenides, especially Sb2S3, by facile and area scalable in-air chemical methods, such as spray pyrolysis, from cost-effective chemicals is certain to accelerate development of the related thin film solar cell technology. In this study, antimony ethyl xanthate, a scarcely studied halogenide-free precursor, is proven to be suitable for the deposition of conformal phase pure crystalline Sb2S3 thin films via ultrasonic spray pyrolysis in air by a two-step process. First, a solution of antimony ethyl xanthate with thiourea in a molar ratio of 1/3, or with thioacetamide in a molar ratio of 1/10 was sprayed onto a glass/ITO/TiO2 substrate by ultrasonic spray pyrolysis at 215°C to yield amorphous phase pure Sb2S3 thin films. Second, performing post-growth heat treatment in vacuum at 225°C, was the key to produce phase pure conformal thin films of crystalline Sb2S3 (Eg 1.8 eV) with S/Sb atomic ratio of 1.46 by using thiourea, and 1.41 by using thioacetamide, respectively. Spraying solutions of antimony ethyl xanthate at ≥135°C resulted in the formation of the Sb2O3 phase. Adding thiourea or thioacetamide to the spray solution prevented the oxidation of the growing Sb2S3 layer during deposition at 135°C, 165°C, and 215°C. The suppressed oxidation of Sb2S3 layers is attributed to the liquid state of thiourea and thioacetamide in these conditions.