Calcium stannate (CaSnO 3 ) is an inorganic perovskite material with an ultrawide bandgap (4.2−4.4 eV) that is associated with its unique structural characteristics. Owing to its remarkable optical and electric properties and high physical and chemical stability, it has recently drawn significant interest for various applications such as photocatalysts for the degradation of organic compounds and hydrogen production under UV radiation, gas sensors, and thermally stable capacitors. In this study, we demonstrate a self-powered deep-UV (DUV) p-i-n photodetector consisting of CaSnO 3 thin film as an efficient DUV absorber via a low-temperature solution process. The physical, optical, and electrical properties of the as-synthesized CaSnO 3 are characterized by X-ray diffraction, Raman spectroscopy, scanning electron microscopy, high-resolution transmission electron microscopy, ultraviolet−visible spectroscopy, photoluminescence spectroscopy, space charge limited current, and four-point probe measurements. As a key component in a pi-n DUV photodetector, the thickness of the CaSnO 3 absorber layer and operating bias are optimized to enhance charge carrier transport, light absorption, and signal-to-noise ratio. As a result, the optimized device shows a high performance at zero bias under 254 nm UV illumination: with a specific detectivity of 1.56 × 10 10 Jones, fast rise/fall time of 80/70 ms, and high 254:365 nm photocurrent rejection ratio of 5.5 along with a stable photoresponse during 100 continuous cycles initially as well as after 1 month of storage. Accordingly, this study suggests that a novel CaSnO 3 -based photodiode prepared via a solution process can be employed for many practical DUV-detection applications.
Zirconium‐benzenedicarboxylate (ZrBDC) is a remarkably stable metal‐organic framework with a broadband UV absorption that would offer numerous applications related to UV detection. However, the integration of a continuous and densely packed ZrBDC film with the controllable thickness into optoelectrical devices suffers from time‐consuming and complicated fabrication of ZrBDC thin film. In this study, a facile liquid‐phase epitaxy method is introduced by adopting sequential and continuous layer‐by‐layer spin‐coating technique to fabricate the high‐quality ZrBDC thin film. The structural, optical, and electrical properties of the as‐prepared ZrBDC thin film are characterized by X‐ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, ultraviolet‐visible spectroscopy, photoluminescence spectroscopy, space charge limited current, and Mott‐Schottky measurement. When ZrBDC is used as an efficient photo‐absorber layer for a visible‐blind UV photodetector, the device exhibits a specific detectivity of 7.85 × 1010 Jones and rise/fall time of 80/150 ms at zero bias. Furthermore, the device reveals outstanding stability with nearly constant photoresponse during 19 h‐exposure to UV illumination and after storing for 2 months, along with excellent tolerance under high operating temperature and bending strain. For practical applications, the facile estimation of UV level under sunlight is demonstrated using a wearable UV detector based on ZrBDC.
Sunlight-originated ultraviolet B (UVB) rays influence daily life in both beneficial and detrimental ways, depending upon light power and exposure time. Therefore, precise and timely UVB irradiance control is of great importance to humans. This study proposes a self-powered and wearable zinc sulfide (ZnS) nanoparticle (NP)-based UVB-C detector for the in situ monitoring of UVB levels in ambient environments. The performance of the ZnS-based photodetector can be markedly enhanced by constructing a vertical p-n heterojunction for testing the feasibility of a self-powered UVB-C detector, employing a thin polyethylenimine (PEI) film for inhibiting current leakage and charge recombination, and introducing a poly(9,9-dioctylfluorene-alt-N-[4-s-butylphenyl]-diphenylamine) (TFB) film as a hole transport layer to increase the photocurrent and enhance the response speed. In particular, we demonstrate that the ZnS NP/TFB junction in the device enables the direct monitoring of narrow and specific UVB bands from sunlight owing to its unique energy band structure and light absorption characteristics. The optimized device has a fast rise/fall time of 50/62 ms, high specific detectivity of 8.20 Â 10 10 Jones, and good stability over long-term storage and against mechanical bending under 254-nm light illumination. Our study provides new insights into self-powered devices that can be implemented for the facile, precise, and rapid estimation of UVB levels under sunlight for various personal healthcare applications.
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