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[Display omitted] • Large-area Bi 2 O 2 Se film composed of many single crystal nanosheets was synthesized. • The layered Bi 2 O 2 Se film features a sharp interface with the SrTiO 3 substrate. • Bi 2 O 2 Se photodetector exhibits excellent cycling stability and long-term stability. • Bi 2 O 2 Se photodetector displays good imaging capability and rapid light extraction. Two-dimensional (2D) materials have proven to be a highly promising candidate for applications in electronic and optoelectronic devices due to their attractive structure and properties. However, the micron-scale dimensions, random distribution on the substrate, and complex transfer processes of 2D materials inevitably cause difficulties in device integration, which limits practical applications in photodetection. Herein, high-quality 2D Bi 2 O 2 Se film (2×2 cm) composed of numerous single crystal nanosheets on SrTiO 3 substrate was prepared employing the chemical vapor deposition method. The layered Bi 2 O 2 Se film features a perfect atomic alignment free of lattice mismatch and a sharp interface with the SrTiO 3 substrate. Afterward, a broadband photodetector based on 2D Bi 2 O 2 Se film was directly constructed, which covered the ultraviolet, visible and infrared range from 365 to 940 nm and demonstrated a fast response speed of 32 ms and 44 ms, maximum responsivity and detectivity of 136 mA/W and 2×109 Jones. Importantly, fast on/off behavior for 100 cycles and reliable photoresponse after storage in air for 1 year confirmed the excellent cycling stability and air stability of the Bi 2 O 2 Se photodetector. Furthermore, the Bi 2 O 2 Se photodetector as a single point sensing pixel was capable to perform high-resolution imaging of "H, I, T" patterns. This research affirms the huge potential of Bi 2 O 2 Se photodetectors to perform as reliable multi-band detection units in complex systems. [ABSTRACT FROM AUTHOR]

By adopting the alkali metal sodium ion (Na+) doping strategy, the grain size of Cs 3 Bi 2 I 9 (CBI) thin film is significantly increased and the non-radiative recombination defects are effectively passivated. Therefore, the self-powered broadband detection performance of photoelectrochemical detector based on the high-quality CBIN x thin films is greatly enhanced. [Display omitted] • Defect passivated lead-free Cs 3 Bi 2 I 9 polycrystalline perovskite thin film was prepared by alkali metal sodium cation doping. • A simple self-powered broadband photoelectrochemical detector based on Cs 3 Bi 2 I 9 thin film was fabricated. • The detector exhibits excellent photodetection performance without bias at UV, visible and near-infrared region. All-inorganic lead-free bismuth-based perovskites have attracted great interest in the optoelectronic applications due to their low toxicity and excellent stability. However, the inherent polycrystalline (PC) of perovskite films suffers severe charge recombination due to the large numbers of trap density. Herein, high-quality Cs 3 Bi 2 I 9 (CBI) PC thin films are prepared by solution process with alkali sodium (Na+) cation doping strategy, resulting large grain size and lower trap density. Afterward, the photoelectrochemical-type detectors based on Na+ doped CBI thin film is constructed for the first time. The photodetector displays a broadband photoresponse covering ultraviolet (UV), visible and near-infrared (NIR) ranges. Significantly, by precisely controlling Na+ doping concentration, the performance of photodetector can be largely enhanced with the highest responsivity of 53.38 mA/W and detectivity of 5.99 × 109 Jones without bias, and these results exceed the performance of most reported CBI PC thin film based photodetectors. In addition, the photodetector exhibits an obvious increase in photoresponse and outstanding photo-stability after more than 150 on/off cycles. Finally, the mechanism of Na+ doping is further discussed. These results provide an outstanding example for the preparing high-quality CBI PC thin film and also demonstrate the great potential of CBI in the application of self-powered broadband photodetectors. [ABSTRACT FROM AUTHOR]

Traditional photoelectrochemical-type (PEC-type) photodetectors have encountered several obstacles in practical application, such as the loss of photoelectrons due to interface charge recombination, short-term performance, and the problem of liquid electrolyte leakage. Herein, a novel quasi-solid-state polysulfide gel electrolyte (QSSPGE) is developed through the integration of liquid polysulfide into the polyvinyl alcohol (PVA) gel matrix. The PVA gel plays the dual function of passivating the surface trap states of bismuth telluride (Bi 2 Te 3) nanosheets and suppressing the leakage and volatilization of the liquid polysulfide electrolyte. Impressively, the PEC-type Bi 2 Te 3 photodetector based on the QSSPGE exhibits a boosted responsivity of 4.91 mA W−1 and a fast rise/decay time of 14/99 ms under 365 nm illumination, outperforming the responsivity (4.32 mA W−1) of PEC-type Bi 2 Te 3 photodetector based on liquid polysulfide. More importantly, the photocurrent density of the device remains at 95% and 81% of the initial value after being stored in air for one month and heated at 80 ℃ for 240 min, respectively, demonstrating excellent long-term stability and thermal stability. Additionally, the high-resolution imaging capacity of the device is demonstrated. This work provides an effective strategy for fabricating high-performance, stable PEC-type optoelectronic devices. [Display omitted] • A novel quasi-solid-state polysulfide gel electrolyte (QSSPGE) is developed. • Interface charge recombination between Bi 2 Te 3 and QSSPGE is suppressed. • Responsivity of the device is boosted from 4.32 mA W−1 to 4.91 mA W−1. • The device based on QSSPGE exhibits excellent thermal and long-term stability. • The stable imaging capacity of the device is demonstrated. [ABSTRACT FROM AUTHOR]