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Band alignment engineering in 2D van der Waals heterostructures is a promising method for manufacturing high‐speed, high‐responsivity, and high‐gain photodetectors. Here, a heterojunction photodetector with the band alignment transition from type I to type II under the bias voltage using narrow bandgap material n‐Bi2Se3 and polarization‐sensitive material p‐GeSe is designed and prepared. This photodetector possesses excellent performance of broadband detection (532‐1550 nm), high responsivity (5.86 × 103 A W−1), high detectivity (1.50 × 1013 Jones), significant external quantum efficiency (1.15 × 106%) and fast response time (97 µs). Compared with the conventional type II band alignment, an additional triangular potential barrier is generated in this type II band alignment evolved from type I. Notably, this triangular barrier will block photogenerated carriers in Bi2Se3, which leads to high external quantum efficiency; Furthermore, photogenerated holes can tunnel through this barrier, effectively shortening the response time. Meanwhile, the device can achieve polarization detection (anisotropic ratio = 1.74 at 808 nm) and polarization imaging, which is of great significance for reducing the bit error rate in complex environments. [ABSTRACT FROM AUTHOR]

Halide perovskites are widely explored as efficient photoresponsive materials for optoelectronic devices. However, understanding and controlling their underlying optical and electrical properties remains limited. Here, a novel approach is developed by introducing silver sulfide (Ag2S) quantum dots (QDs) into an MAPbBr3 single crystal. The high‐quality Ag2S‐quantum‐dot‐in‐perovskite (Ag2S‐QDiP) matrixes synthesized through a laser‐assisted inverse temperature crystallization (LA‐ITC) strategy show broadband light‐sensitive wavelength from 550 to over 1000 nm, and a balanced carriers mobility facilitates their transmission and collection. A Ag2S‐QDiP‐enabled photodetector is demonstrated, which exhibits considerably enhanced responsivity and detectivity of 1.17 A W−1 and 6.24 × 1014 Jones at 532 nm, and 57.69 mA W−1 and 1.03 × 1011 Jones at 1064 nm, respectively. The enhanced performance in the near‐infrared (NIR) region can be attributed to the discrete heterojunction formed between MAPbBr3 and Ag2S QDs, which enhances the light absorption in the NIR range and facilitates photogenerated excitons' separation at the interface. The facile synthesis process, the more balanced transport behavior, and the ensuing improved device performance highlight introducing QDs into perovskite single crystal as an efficient strategy for tuning fundamental properties of perovskite and for developing high‐efficiency broadband electronic and optoelectronic devices. [ABSTRACT FROM AUTHOR]

Despite its extensive research in photovoltaics and light emitting diodes, the charge transport properties of all‐inorganic perovskite cesium lead bromide (CsPbBr3) remain elusive. Clarification of the intrinsic charge transport of this perovskite material is highly desirable, which will help to understand its working mechanism and fabricate high performance electronic devices. Here, it is demonstrated that the phototransistors based on CsPbBr3 microplates show anomalous ambipolar transport characteristics at room temperature. The hole mobility shows light dependence, while the electron mobility is identical under various light incidence. The hole mobility increases from 0.02 cm2 V−1 s−1 (in dark conditions) to 0.34 cm2 V−1 s−1 (50 mW cm−2); while the threshold voltage is shifted by 14 V when electron is the majority charge carrier. The anomalous transport behavior can be attributed to the photovoltaic and photoconductive effects. Moreover, the device shows photoresponsivity and detectivity up to 110 mA W−1 and 4.5 × 1013 Jones, respectively, under 532 nm laser illumination. This research unveils the charge transport mechanism of CsPbBr3 perovskite, provides more evidence and will thus contribute to the perovskite electronic and optoelectronic researches. [ABSTRACT FROM AUTHOR]

Single crystal perovskites are used in solar cells, photodetectors, and other devices due to their excellent light absorption and carrier transport characteristics. However, for light‐emitting applications, photoluminescence (PL) is usually weak for MAPbBr3 (MA = CH3NH3+) single crystals (MBSCs) compared with their polycrystalline counterpart. Therefore, developing novel techniques to process MBSCs with different morphologies for PL‐related applications is greatly needed. The current strategies for making perovskite crystals are mostly based on bottom‐up method (chemical synthesis and assembling). Here, an easy method to achieve top‐down fabrication of MBSCs, i.e., femtosecond laser processing MBSC surface by controlling the laser parameters is demonstrated. The femtosecond laser processing technology can achieve two orders of magnitude enhancement under ambient conditions in PL. In addition, the processed regions also show three times enhancement in PL under nitrogen environment. It is assumed that this is mainly due to the texture based on photon recycling and light out‐coupling mechanism, and the passivation of surface recombination centers on MBSC. This study not only provides a convenient top‐down strategy to achieve a range of morphological micro‐/nanostructures with enhanced PL on MBSC surface, but also paves the way for applications of MBSCs in light emitting or PL imaging devices. Developing novel techniques to process MAPbBr3 single crystals (MBSCs) with various morphologies for photoluminescence‐related applications is highly necessary. Multi‐morphological micro‐/nanostructures induced by a top‐down fabricating technology, i.e., femtosecond laser processing, are achieved on MBSC surfaces. Dramatically‐enhanced photoluminescence of two orders of magnitude in ambient conditions and three times in nitrogen atmosphere is demonstrated, which is promising for photoluminescence‐related applications. [ABSTRACT FROM AUTHOR]