Polycrystalline thin films of (Sb<sub>0.42</sub>Bi<sub>0.58</sub>)<sub>2</sub>Se<sub>3</sub> are prepared by co-evaporation in a two-step process. First, the semiconducting layer is grown at 240°C. Subsequently the films are annealed in-situ at various temperatures. The incorporation of Bi into the orthorhombic Sb<sub>2</sub>Se<sub>3</sub> system reduces the bandgap and thus widens the range for infrared detection. It is found that thin film layers can be prepared single phase, while a decomposition is observed for temperatures exceeding 440°C, where the rhombohedral structure of Bi<sub>2</sub>Se<sub>3</sub> forms in addition. Photoluminescence measurements show an increased optoelectronic quality of the films with increasing annealing temperature. However, the luminescence signal reduces when the films decompose into the orthorhombic and the rhombohedral phases.