Antimony sulfide thin films in chemically deposited thin film photovoltaic cells

Antimony sulfide thin films of thickness ∼ 500 nm have been deposited on glass slides from chemical baths constituted with SbCl3 and sodium thiosulfate. Smooth specularly reflective thin films are obtained at deposition temperatures from - 3 to 10 deg. C. The differences in the film thickness and improvement in the crystallinity and photoconductivity upon annealing the film in nitrogen are presented. These films can be partially converted into a solid solution of the type Sb2S xSe3-x, detected in X-ray diffraction, through heating them in contact with a chemically deposited selenium thin film. This would decrease the optical band gap of the film from ∼ 1.7 eV (Sb2S3) to ∼ 1.3 eV for the films heated at 300 deg. C. Similarly, heating at 300 deg. C of sequentially deposited thin film layers of Sb2S3-Ag2Se, the latter also from a chemical bath at 10 deg. C results in the formation of AgSb(S/Se)2 with an optical gap of ∼ 1.2 eV. All these thin films have been integrated into photovoltaic structures using a CdS window layer deposited on 3 mm glass sheets with a SnO2:F coating (TEC-15, Pilkington). Characteristics obtained in these cells under an illumination of 850 W/m2 (tungsten halogen) are as follows: SnO2:F-CdS-Sb2S3-Ag(paint) with open circuit voltage (Voc) 470 mV and short circuit current density (J sc) 0.02 mA/cm2; SnO2:F-CdS-Sb2S3-CuS-Ag(paint), Voc ∼ 460 mV and J sc ∼ 0.4 mA/cm2; SnO2:F-CdS-Sb2S xSe3-x-Ag(paint), Voc ∼ 670 mV and Jsc ∼ 0.05 mA/cm2; SnO2:F-CdS-Sb2S3-AgSb(S/Se)2-Ag(paint), Voc ∼ 450 mV and Jsc ∼ 1.4 mA/cm2. We consider that the materials and the deposition techniques reported here are promising toward developing 'all-chemically deposited solar cell technologies.'