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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. [ABSTRACT FROM AUTHOR]

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%. [ABSTRACT FROM AUTHOR]

The Ag-alloyed Cu 1.9 Ag 0.1 ZnSn(S,Se) 4 (CAZTSSe) films were prepared by selenidation of Cu 1.9 Ag 0.1 ZnSnS 4 (CAZTS) precursor films under various selenidation conditions. The effects of selenidation time and selenidation temperature on the composition, morphology, optical band gap (Eg) and device performance of CAZTSSe films were systematically studied. It is found that the selenidation temperature of 480 °C and selenidation time of 10 min provide a favorable selenidation environment for the growth of the film, which can promote grain growth and form a thick and smooth film. This has been strongly confirmed through relevant tests. In addition, the analysis of performance characterization of the films shows that the Eg of the films can be adjusted via adjusting the selenidation conditions, so as to improve the electrical properties. Finally, the CAZTSSe solar cell with a photoelectric conversion efficiency (PCE) of 5.94 % and an open circuit voltage (V oc) of 397 mV was successfully prepared at the selenidation temperature of 480 °C and selenidation time of 10 min. • A new method to improve V oc and PCE of CZTSSe solar cell by Ag doping is put forward. • This is the first report on the effect of post-selenization on CAZTSSe solar cell. • Eg of CAZTSSe can be continuously adjusted by adjusting the selenidation condition. • The effect of selenization condition on PCE is ascribed to change of V OC and FF. • This study shows hopeful character of selenidation condition in increasing the PCE. [ABSTRACT FROM AUTHOR]

In this work, the Cu2MnxZn1−xSn(S,Se)4 (0 ≤ x ≤ 1) (CMZTSSe) alloy films were fabricated by a sol-gel method. Meanwhile, the effects of Mn substitution on the structural, morphological, electrical, optical, and device performance were studied systematically. The clear phase transformation from Cu2ZnSn(S,Se)4 (CZTSSe) with kesterite structure to Cu2MnSn(S,Se)4 (CMTSSe) with stannite structure was observed as x = 0.4. The scanning electron microscope (SEM) results show that the Mn can facilitate the grain growth of CMZTSSe alloy films. Since the x was 0.1, the uniform, compact, and smooth film was obtained. The results show that the band gap of the CMZTSSe film with a kesterite structure was incessantly increased in a scope of 1.024–1.054 eV with the increase of x from 0 to 0.3, and the band gap of the CMZTSSe film with stannite structure was incessantly decreased in a scope of 1.047–1.013 eV with the increase of x from 0.4 to 1. Meanwhile, compared to the power conversion efficiency (PCE) of pure CZTSSe device, the PCE of CMZTSSe (x = 0.1) device is improved from 3.61% to 4.90%, and about a maximum enhanced the open-circuit voltage (VOC) of 30 mV is achieved. The improvement is concerned with the enhancement of the grain size and decrease of the Cu instead of Zn (CuZn) anti-site defects. Therefore, it is believed that the adjunction of a small amount of Mn may be an appropriate approach to improve the PCE of CZTSSe solar cells. [ABSTRACT FROM AUTHOR]

Owing to open-circuit voltage (V OC) deficits, Cu 2 ZnSn(S,Se) 4 (CZTSSe) alloy film solar cells have limited improvements in device performance. Cation replacement in CZTSSe absorbers is key in studying the enormous potential of kesterite solar cells and thus in developing cost-effective photovoltaic technology. In this study, Cu 2 Cr x Zn 1−x Sn(S,Se) 4 (0 ≤ x ≤ 0.2) (CCZTSSe) films were prepared using solution-processing and a two-step annealing technique. The device properties and effects of Cr-doping on the structure, morphology, and optoelectrical performance of the CCZTSSe films were investigated. The results showed that appropriate Cr-doping promotes grain growth, which enables the production of compact CCZTSSe films with larger grain sizes and fewer holes. In addition, the significantly enhanced absorption of the CCZTSSe thin films indicates the presence of intermediate bands (IB) in the band gaps, which promotes the absorption of low-energy photons. Cr-doping can also reduce the Cu Zn antisite defects. Finally, the efficiency of the CCZTSSe (x = 0.1) device was enhanced from 3.74 % to 5.44 %, and the V OC was boosted from 0.35 V to 0.39 V, compared to the pure CZTSSe (x = 0) device. These findings pave the way for improvements in the efficiency of CZTSSe devices. • This is the first report on the fabricating Cr-doped CZTSSe cell by solution-process. • Cr doping can introduce intermediate band to promote absorption of low-energy photon. • This study shows hopeful character of Cr in increasing the Voc of CZTSSe solar cell. • Cr doping can improve crystal quality and decrease the Cu Zn antisite defect states. • It is proved that Cr-doped CZTSSe is a promising band-gap tunable absorption layers. [ABSTRACT FROM AUTHOR]