Composition dependence of the structure and optical properties of Cu2MnxZn1−xSnS4 thin films

•Cu2MnxZn1−xSnS4 (CMZTS) thin film have been firstly prepared by sol–gel technique.•XRD and Raman demonstrate the structural transition from kesterite to stannite with increasing Mn content.•The band gap energy of CMZTS thin films can be tuned almost linearly between 1.23 and 1.51 eV varying with Mn compositions.

Cu2Zn1−xMnxSnS4 (CMZTS) thin films with composition controllability and tunable band gap have been firstly prepared by sol–gel technique followed by a post-annealing treatment at 580 °С for 10 min in nitrogen gas atmosphere. Effects of Mn variation in CMZTS thin films with x = 0.0–1.0 on the morphological, structural, and optical properties have been investigated. XRD and Raman studies reveal the incorporation of Mn into Cu2ZnSnS4 (CZTS) thin films, and demonstrate the structural transition from kesterite to stannite with increasing Mn content. SEM images show that compact, homogeneous and densely packed grains could be formed. Furthermore, UV–vis spectroscopy indicate that the band gaps of the CMZTS films can be tuned almost linearly between 1.23 and 1.51 eV with a small bowing constant of the band gap (∼0.10 eV), which confirms the good miscibility of the alloyed constituents in the crystal lattice.