All-inorganic perovskite CsPbX3 (X = Cl, Br, and I) quantum dots (QDs) are emerging as attractive materials for photodetectors due to their prominent positive photoresponse. In this work, ambipolar photodetectors were constructed based on heterojunctions of CsPbX3 QDs and ZnO nanocrystals (NCs). The transition between the positive photoconductivity (PPC) and negative photoconductivity (NPC) was successfully controlled not only by the drain-source voltage (V DS) but also by the excitation wavelength and CsPbX3 crystal size. A high responsivity (R), on–off ratio (η), and detectivity (D*) were achieved for NPC (R = 1046 mA/W, η = 281, and D* = 1.65 × 1011 Jones), with PPC (R = 146 mA/W, η = 64, and D* = 1.54 × 1011 Jones) simultaneously revealed in the same device. A general mechanism combining the type-II heterojunction, the component and size-related band structure, and most critically the in-band trap states of the perovskites was established for understanding the unique ambipolar property. It exhibits application potential in developing functional photodetectors, memristors, and optical logic devices.

No abstract

The quality and property control of nanomaterials are center themes to guarantee and promote their applications. Different synthesis methods and reaction parameters are control factors for their properties. However, the vast combination number of the factors with multilevels leads to the obstacle that trying all‐through the data space is nearly impossible. Herein, the combination of microfluidic synthesis method with machine learning (ML) models to address this challenge in case of perovskite quantum dots (PQDs) with tunable photoluminescence (PL) is reported. The ML‐assisted synthesis not only helps to elucidate the nucleation growth‐ripening mechanisms, but also successfully guides to synthesize PQDs with precise wavelength and full width of half maximum (FWHM) of the PL by optimizable conditions to match the time‐saving, energy‐saving, and minimal environmental pressure goals.

As a narrow band semiconductor at room temperature and a metallic material above ∼68 °C, functional VO2 films are widely investigated for smart windows, whereas their potential for ultraviolet–visible–infrared (UV–vis–IR) broad spectral photodetectors has not been efficiently studied. In this report, photodetectors based on VO2–ZnO nanocrystal composite films were prepared by nanocrystal-mist (NC-mist) deposition. An enhanced photodetection switching ratio was achieved covering the ultraviolet to infrared wavelength. Due to the synergetic effect of nanosize, surface, phase transition, percolation threshold, and the band structure of the heterojunction, the transfer and transport of photogenerated carriers modulate the device performance. This study probes new chances of applying VO2-semiconductor-based nanocomposites for broad spectral photodetectors.

No abstract