Facile solution-based fabrication of ZnIn2S4 nanocrystalline thin films and their photoelectrochemical properties

• Hexagonal ZnIn2S4 nanocrystalline thin films are deposited by spin-coating method.
• ZnO and In(OH)3 are dissolved by thioacetic acid in precursor solution.
• ZnIn2S4 nanocrystals preferentially grow along c-axis via annealing in S vapor.
• ZnIn2S4 films show pronounced photoelectrochemical response under visible light.

Hexagonal phase ZnIn2S4 nanocrystalline thin films are deposited by spin-coating method using an air-stable precursor solution. In the process, metal oxide and hydroxide are used as Zn and In sources to avoid the introduction of any anion impurity in ZnIn2S4 thin films. The rod-like nanocrystalline grains with width and length about 13 ± 3 nm and 26 ± 5 nm grow along c-axis after annealing in sulfur vapor at 500 °C for 2 h. Smooth and compact thin films with different In/Zn ratios are fabricated by controlling the ratio of two metal sources in precursor solution. The flat-band potentials of these n-type ZnIn2S4 thin films are in the range of −0.55 to −0.45 V vs. normal hydrogen electrode. The photoelectrochemical measurement demonstrates the excellent visible light response of ZnIn2S4 thin films. The light current under visible light illumination occupies almost 60% of the light current under full spectrum illumination. The facile solution-based method provides a novel thought to fabricate high-quality thin films of multi metal chalcogenides with excellent photoelectric properties via solving the other metal oxide and hydroxide in the solution.