The Cu 2 Ni x Zn 1−x Sn(S,Se) 4 (0 ≤ x ≤ 0.1) (CNZTSSe) film absorbing layer materials were successfully prepared by sol−gel means and post selenization technique. The experimental results show that the crystal quality, photoelectric properties, and device efficiency of the film can be improved by Ni doping. The grain size and crystallinity of the films significantly increase by adjusting the doping content of Ni. When x = 0.05, crystallinity and grain size reach the optimum value, and the film surface is smooth and compact. Meanwhile, Ni has successfully replaced the Zn site in the crystal lattice, which reduces the formation of harmful defects related to Zn and improves the electrical properties of the films. The hole concentration of the film is 5.03 × 10 14 cm −3 , and the maximum Hall mobility of the film is 8.95 cm 2 V −1 s −1 under the optimum Ni doping content (x = 0.05). In addition, the continuously tunable band gap (E g ) was obtained, which decreases continuously from 1.17 to 1.08 eV. Compared with the pure Cu 2 ZnSn(S,Se) 4 (CZTSSe) solar cell, the open circuit voltage (V OC ) of the CZNTSSe (x = 0.05) device was increased by 42 mV, and the power conversion efficiency was boosted from 3.61 to 5.32%. KEYWORDS: thin films, Cu 2 Ni x Zn 1−x Sn(S,Se) 4 , sol−gel, photoelectric properties, solar cells

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The Cu2Ni0.05Zn0.95Sn(S,Se)4 (CNZTSSe) films were synthesized by sol-gel combined with selenidation treatment. To further enhance the crystal quality of the film, the selenidation conditions were optimized, and the effects of selenidation time on the properties of the CNZTSSe films and devices were systematically studied. The results show that the crystallinity of the films increased remarkably with the increase of selenidation time. Under the optimum selenidation time of 15 min, smooth and dense films were obtained. Through the analysis of EDS results, it is found that Se occupies more S positions with the increase of selenidation time, which decreases the band gap of the film from 1.14 eV to 1.0 eV. In addition, the formation of Zn-related defects is effectively suppressed by Ni doping to enhance the open circuit voltage (Voc) of the CNZTSSe solar cells. When the selenidation time is 15 min, the CNZTSSe film has the highest carrier concentration of 1.68 × 1016 cm−3, and the best efficiency of the device prepared based on the film as the absorption layer is 5.0%, and the Voc is 337 mV.

Cu2Ni0·05Zn0·95Sn(S,Se)4 (CNZTSSe) films were synthesized on Mo-coated glass substrates by the simple sol–gel means combined with the selenization process, and CNZTSSe-based solar cells were successfully prepared. The effects of selenization temperature on the performance and the photoelectric conversion efficiency (PCE) of the solar cells were systematically studied. The results show that the crystallinity of films increases as the selenization temperature raises based on nickel (Ni) doping. When the selenization temperature reached 540 °C, CNZTSSe films with a large grain size and a smooth surface can be obtained. The Se doping level gradually increased, and Se occupied the S position in the lattice as the selenization temperature was increased so that the optical band gap (Eg) of the CNZTSSe film could be adjusted in the range of 1.14 to 1.06 eV. In addition, the Ni doping can inhibit the deep level defect of SnZn and the defect cluster [2CuZn + SnZn]. It reduces the carrier recombination path. Finally, at the optimal selenization temperature of 540 °C, the open circuit voltage (Voc) of the prepared device reached 344 mV and the PCE reached 5.16%.