Composition Engineering for the Content and Distribution of Sb–O, Se, S in Antimony Sulfoselenide Thin Films Using Chemical Bath Deposition for Efficient Solar Cells

Herein, Na 2 SSeO 3 solutions are prepared by hydrothermal method at 140 °C for 8 h using Se powder and Na 2 SO 3 solution (the molar ratios of Se:Na 2 SO 3 = 1:4, 1:5, 1:6) and the chemical composition of Na 2 SSeO 3 solutions is analyzed by X‐ray photoelectron spectroscopy. Sb 2 S y Se 3− y thin films are prepared by chemical bath deposition (CBD) at 90 °C for 5 h and subsequently annealed at 375 °C for 10 min and etched by N ‐butyldithiocarbamic acid solution in DMF. The effect of the Na 2 SSeO 3 solution, growth solution volume, etching on the thickness and chemical composition of Sb 2 S y Se 3− y thin films, and the power conversion efficiency (PCE) of the corresponding solar cells is systematically investigated. The result reveals that the Na 2 SSeO 3 solutions may be the mixing solutions containing Na 2 SSeO 3 , Na 2 S 2 SeO 6 , Na 2 S 2 Se 2 O 6 , Na 2 Se. When the molar ratio of Se:Na 2 SO 3 and growth solution volume is 1:5 and 56 mL and the Sb 2 S y Se 3− y thin films with annealing are etched, the PCE of Sb 2 S y Se 3− y solar cells is 8.00% with spiro‐OMeTAD and 8.43% with spiro‐OMeTAD:TMT‐TTF. The PCE of 8.43% is the highest value for Sb 2 S y Se 3− y solar cells using CBD and demonstrates that the composition engineering is an important strategy for improving the PCE of Sb 2 S y Se 3− y solar cells using CBD.