Chalcogenide Cu 2 ZnSn(S,Se) 4 (CZTSSe) is a promising absorber material for photovoltaic applications. When CZTSSe thin film is deposited on an Mo substrate, a Mo(S,Se) 2 layer easily forms between the CZTSSe and the Mo, which is detrimental to the back contact property of the CZTSSe. This work proposes a useful way to inhibit the formation of Mo(S,Se) 2 by sputtering a CuCrO 2 layer on a Mo-foil substrate before the deposition of the CZTSSe. The effects of CuCrO 2 thickness on the crystalline structures, morphologies, and electrical properties of the fabricated samples were studied. The results showed that the insertion of the CuCrO 2 layer prevented the formation of Mo(S,Se) 2 . As the thickness of the CuCrO 2 increased, the thickness of the Mo(S,Se) 2 layer decreased. The Mo(S,Se) 2 layer was absent from the cross-sectional scanning electron microscopy image when the CuCrO 2 thickness exceeded 85 nm. The back contact resistance of CZTSSe decreased monotonously as the CuCrO 2 layer thickened due to the reduction in the Mo(S,Se) 2 layer thickness. Therefore, by inserting a CuCrO 2 layer to separate the CZTSSe and the Mo-foil, the formation of the Mo(S,Se) 2 layer between them was effectively suppressed, and the back contact properties of the CZTSSe thin film were significantly enhanced.
Visible and near-infrared photodetectors are widely used in intelligent driving, health monitoring, and other fields. However, the application of photodetectors in the near-infrared region is significantly impacted by high dark current, which can greatly reduce their performance and sensitivity, thereby limiting their effectiveness in certain applications. In this work, the introduction of a C 60 back interface layer successfully mitigated back interface reactions to decrease the thickness of the Mo(S,Se) 2 layer, tailoring the back-contact barrier and preventing reverse charge injection, resulting in a kesterite photodetector with an ultralow dark current density of 5.2 × 10 −9 mA/cm 2 and ultra-weak-light detection at levels as low as 25 pW/cm 2 . Besides, under a self-powered operation, it demonstrates outstanding performance, achieving a peak responsivity of 0.68 A/W, a wide response range spanning from 300 to 1600 nm, and an impressive detectivity of 5.27 × 10 14 Jones. In addition, it offers exceptionally rapid response times, with rise and decay times of 70 and 650 ns, respectively. This research offers important insights for developing high-performance self-powered near-infrared photodetectors that have high responsivity, rapid response times, and ultralow dark current.
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