Spin-coated Cu2CrSnS4 thin film: A potential candidate for thin film solar cells

Abstract

In this regard for the first time, the multicomponent chalcogenide Cu2(Zn1-xCrx)SnS4 (CZCrTS) nanocrystals at (0 ≤x ≤ 1) were synthesized by the solvothermal method. Improvement of structural, optical and electrical properties in Cr-doped Cu2ZnSnS4 thin film deposited on SLG substrate by spin coating technique has been investigated. It was observed that introduced the Cr element into the Cu2ZnSnS4 nanocrystal led to increasing the disorder of cations distribution within the unit cell through increasing the tensile strain inside the unit cell resulting in a decline the unit cell volume accompanied by a decrease the particle size and also the crystallite size. It has been found that the optical band gap of the CZCrTS nanocrystals ranges from 1.54 to 1.35 eV with increasing the partial substitution of Zn element with Cr element which in turn also led to a significant improvement in the crystallinity of the Cu2ZnSnS4 film, a facilitates the grain growth and also increases the grain size where accompanied this process post-sulfurization at 450 ℃ for 30 min. In addition, it was observed that the number of grains in the Cu2CrSnS4 film (x = 1), 2.79 (nm−2), were lower than that, 6.8 (nm−2) of the Cu2ZnSnS4 film. Also, the dislocation density in the Cu2CrSnS4 film (x = 1), 0.012 (nm−2), was lower than that, 0.024 (nm−2) of the Cu2ZnSnS4 film, which resulted in decreased the defects in the grain boundaries and increasing the current from 0.34 mA for the Cu2ZnSnS4 film to 0.42 mA for the Cu2CrSnS4 film. Due to a higher absorption coefficient (>104 cm−1), a higher optical conductivity (> 23 *1012 S−1) and lower transmittance have been reported for the Cu2CrSnS4 thin film (x = 1), we believe the Cu2CrSnS4 thin film may be a good candidate can be used as an absorbent layer to sunlight in thin film solar cell.