Thin films of Cu2ZnSnS4 (CZTS), a potential candidate for absorber layer in thin film heterojunction solar cell, have been deposited by spray pyrolysis technique onto soda‐lime glass substrates held at a substrate temperature (Ts) of 643 K. The effect of copper salt and thiourea concentrations on the formation of Cu2ZnSnS4 thin films is investigated. CZTS films formed under optimized conditions are found to be polycrystalline in nature with kesterite structure. The lattice parameters are found to be a = 0.543 nm and c = 1.086 nm. The optical band gap of these films is found to be 1.43 eV. It is found to increase with decrease in copper salt concentration in the solution.

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The effect of substrate temperature and post-deposition annealing on the growth and properties of Cu 2 ZnSnSe 4 thin films, a potential candidate for a solar cell absorber layer, is investigated. The substrate temperature (T s ) is chosen to be in the range 523-673 K and the annealing temperature (T pa ) is kept at 723 K. Powder x-ray diffraction (XRD) patterns of as-deposited films revealed that the films deposited at T s = 523 K and 573 K contain Cu 2−x Se as a secondary phase. Single phase, polycrystalline Cu 2 ZnSnSe 4 films are obtained at T s = 623 K and films deposited at T s = 673 K have ZnSe as a secondary phase along with Cu 2 ZnSnSe 4 . Direct band gap of as-deposited CZTSe films is found to lie between 1.40 eV and 1.65 eV depending on T s . XRD patterns of post-deposition annealed films revealed that the films deposited at T s = 523-623 K are single phase CZTSe and films deposited at T s = 673 K still contain ZnSe secondary phase. CZTSe films are found to exhibit kesterite structure with the lattice parameters a = 0.568 nm and c = 1.136 nm. Optical absorption studies of post-deposition annealed films show that there is a slight increase in the band gap on annealing, due to decrease in the Cu content. Electrical resistivity of the films is found to lie in the range 0.02-2.6 cm depending on T s .

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