Fabrication of $$\text {Cu}_{2}\text {SnS}_{3}$$ Cu 2 SnS 3 films by annealing chemically deposited SnS–CuS precursors in a graphite box

Abstract

Monoclinic $$\text {Cu}_{2}\text {SnS}_{3}$$ (CTS) thin films are prepared by annealing chemically deposited SnS–CuS precursors at 520-580 $$^{\circ }\text {C}$$ in a graphite box under atmospheric ( $$\text {N}_{2}+\text {S}_{2}$$ ) pressure, and the effects of annealing temperature and time on the grain growth and morphology of the films are investigated. The films prepared at 520 and 550 $$^{\circ }{\text{C }}$$ show improvement in grain size and the formation of uniform and compact grains with increasing annealing time. The films prepared at 580 $$^{\circ }\text {C}$$ exhibit good grain growth with grain sizes $$\sim 1.0{-}3.0\,\upmu \text {m}$$ ; however, the grain size does not increase with annealing time. Further, annealing time of 120 min at 550 and 580 $$^{\circ }\text {C}$$ leads to material loss. A small amount of $$\text {Cu}_{4}\text {SnS}_{4}$$ is detected in the films. In addition, annealing the films at 550 and 580 $$^{\circ }\text {C}$$ for 90 min with decreased CuS thickness results in a reduction of $$\text {Cu}_{4}\text {SnS}_{4}$$ phase, homogeneous grain growth with grain sizes of $$2.0{-}3.5\,\upmu \text {m}$$ throughout the film thickness, and hole mobilities in the range of $$6.0{-}5.3\,\text {cm}^{2}\,\text {V}^{-1}\,\text {s}^{-1}$$ . These results demonstrate the effectiveness of this annealing approach for producing high quality CTS films with micron-sized grains, which is useful for improving the efficiency of CTS-based thin film solar cells.