Sol-gel solution-processed Cu2SrSnS4 thin films for solar energy harvesting

According to theory calculation, the Cu2SrSnS4 (CSTS) become a candidate material for harvesting solar energy via either photovoltaic (PV) or photoelectrochemical (PEC) paths due to its efficient light-absorbing capability (high absorption coefficients above 104 cm−1), earth-abundant, nontoxic constituents, and suitable defect properties. As a new material, there is a long way to accomplish the application of CSTS. Film preparation of CSTS are very critical. In this work, CSTS thin films were synthesized by a sol-gel based solution process. The obtained CSTS films showed trigonal structure with band gap of 1.93 eV and p-type conductivity. By comparing the CSTS thin films synthesized with different annealed temperature and Sr/Sn atomic ratios, we confirmed that sulfurization annealing at 600 °C and Sr/Sn atomic ratios of 1.15 yields relatively high quality CSTS films. A PEC cell using the CSTS thin film as working electrode were established and a saturated photocurrent of ∼0.5 mA/cm2 had been achieved. It has also been applied to a PV device, demonstrating open-circuit voltage of 296 mV and power conversion efficiency of 0.164%. Pinholes in the films and reef-like grains at the surface of CSTS films were likely to limit the devices performance. The feasibility of solar energy harvesting of CSTS material was demonstrated.