Water Additive Enhanced Solution Processing of Alloy Sb2(S1−xSex)3‐Based Solar Cells

Solution process is a convenient and cost‐effective approach to the deposition of thin films for optoelectronic devices. The quality of as‐prepared films depends critically on the applied precursor materials as well as solvents. Herein, a method is developed to synthesize Sb 2 (S 1− x Se x ) 3 thin films and demonstrate the role played by water during the film formation. In the synthesis, antimony trichloride, selenourea, and thiourea used as Sb, Se, and S sources are dissolved in N , N ‐dimethylformamide and dimethyl sulfoxide mixed solvents. It is found that a tiny amount of water (1%) in the solution enables an essential increase in grain size that in turn facilitates carrier transport and suppresses recombination. The deep‐level transient spectroscopy analysis shows that water additive helps to reduce defect density and type in the as‐obtained films. Finally, the improved film quality leads to a certified power conversion efficiency of 7.42%, a top efficiency in Sb 2 (S,Se) 3 ‐based solar cells regardless of the device configurations. This study provides an effective approach to tailor the optoelectronic properties of Sb 2 (S,Se) 3 and a practical strategy to improve the device efficiency.