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CsPbCl3‐based inorganic perovskite ultraviolet photodetectors (UV‐PDs) have a great promise for the wide application prospects due to the desirably UV‐matched energy band and the excellent intrinsic optoelectronic properties. However, the traditional high‐temperature Bridgman method (near 600 °C) and complexly time‐consuming vapor preparation (several days) of high‐quality CsPbCl3 crystals have badly restricted its commercial applications to date. Herein, an antisolvent‐induced crystallization kinetics (ACK) strategy is demonstrated for the quick lower‐temperature fabrication (50 °C, tens of minutes) of excellent continuous highly crystalline CsPbCl3 microcrystal films (MCFs) with low trap density (1.42 × 1012 cm−3). Further, the as‐developed CsPbCl3 MCF‐based UV‐PDs present a high detectivity of 5.6 × 1012 Jones, a superior responsivity of 2.11 A W−1, and robust stability. Evidently, this work provides a rapid and simple method to prepare high‐quality perovskite MCFs, greatly promoting the commercial development of perovskite‐based photodetectors. [ABSTRACT FROM AUTHOR]

Low photoluminescence quantum yield (PLQY) and spectra instability, the two most difficult challenges in blue‐emitting CsPbBrxCl3−x NCs, have not yet been solved. Quickly controlling the reaction thermodynamics is crucial to enhance crystallinity, thus PLQY and spectra stability, but it has been ignored until now. An ultrafast thermodynamic control (UTC) strategy is designed by utilizing liquid nitrogen to instantaneously freeze the superior crystal lattices of CsPbBrxCl3−x NCs formed at high temperature. The average cooling rate exhibits a 33‐fold increase compared to conventional ice‐water cooling (from 1.5 to 50 K s−1). This UTC can make the reaction thermodynamic energy of the system lower than the threshold very quickly. Therefore, abrupt termination of further crystal growth can be achieved, which also avoids additional nucleation at low temperature. With the assist of defect passivation, the final blue‐emitting CsPbBrxCl3−x NCs exhibit an absolute PLQY of 98%, representing the highest value in Pb‐based blue perovskites to date. More importantly, they exhibit superior spectra instability. This UTC strategy not only represents a new avenue to synthesize perovskite NCs with excellent crystal quality and ultrahigh PLQY, but also provides a good reference to deal with the recognized bottleneck of spectra instability. [ABSTRACT FROM AUTHOR]

Flexible photodetectors (PDs) are attracting more attention due to their promising applications in wearable optoelectronic devices, bendable imaging sensors, and implantable optoelectronics. For the easy‐processable technology of massively fabricating PDs, instead of the expensive and complex high‐vacuum technique, the well‐matched work function of their active materials is essential. Herein, all‐sprayed‐processable and large‐area PDs are demonstrated on common paper based on two‐dimensional (2D) CsPbBr3 nanosheets and conductive Ti3C2Tx (MXene). Ascribed to the superior conductivity of MXene, high crystallinity of 2D CsPbBr3, and their well‐matched work function, the as‐prepared PDs exhibit an outstanding on/off current ratio up to 2.3 × 103 and a remarkable photoresponse as fast as 18 ms. Specifically, the detectivity (D*) of 6.4 × 108 Jones and responsivity (R) of 44.9 mA W−1 under a bias of 10 V are achieved. Besides, after bending 1500 cycles, the as‐prepared PDs can still maintain the excellent flexibility and stability. Based on this, a superior‐quality and large‐area 1665 pixel sensor in 72 cm2 (≈24 units cm−2) is developed, and it can clearly transmit the image of "0" to realize the photocommunication function. This work provides a low‐cost method of massively producing the flexible large‐area PDs for wearable optoelectronic devices and expanded photocommunication. The on‐paper flexible photodetectors based on 2D perovskite nanosheets and Ti3C2Tx (MXene) as the active materials and electrode materials by all‐spraying method are demonstrated. The low‐cost photodetectors have high stability, flexibility, photoelectric performance, and can effectively realize the optical communication function of image sensing by large‐area arrays. This technique can be potentially expanded to other optoelectronic devices. [ABSTRACT FROM AUTHOR]