Narrowband photodetectors with tunable spectral responses are highly desirable for applications in image sensing, machine vision, and optical communication. Herein, a filterless and self‐driven perovskite narrowband photodetector (PNPD) based on the defect‐assisted charge collection narrowing (CCN) mechanism is reported, which is enabled by a high‐quality thick perovskite film. By adjusting the halide component of the perovskite layer, the bandgap is successfully modulated and the corresponding narrowband photodetectors show a wide spectral response range from the red to the near‐infrared (NIR), all with full‐widths at half maximum (FWHMs) below 30 nm. Specifically, the methylammonium lead iodide (MAPbI3) narrowband photodetector exhibits a characteristic detection peak at 800 nm with a very low noise current of ≈0.02 pA Hz–1/2, a high specific detectivity up to 1.27 × 1012 Jones, and a fast response speed with rise/fall time of 12.7/6.9 µs. Impressively, these values are among the highest of their kind reported previously, and allow demonstration of narrowband imaging. The excellent performance of self‐driven PNPDs lights up their prospect in high‐efficiency optoelectronic devices without external power sources.

No abstract

No abstract

The high cost and difficulty of fabricating high-quality, thick, large-area X-ray absorbers limit their widespread applications in flat-panel direct hard X-ray imaging. Then it comes to the recently rising halide perovskites, which show large carrier mobility and lifetime, contain high atomic number elements and are solution processible, making them ideal for large-area direct hard X-ray imaging. Over the past few years, direct X-ray detectors based on a variety of perovskites have been developed, showing impressive progress in achieving high sensitivity and low detection limit. Alongside the developments, the underlying correlations between the intrinsic properties of the perovskites and their X-ray detection performance have been intensively studied, providing valuable information to tackle the remaining challenges, such as large dark current, baseline drifting and so forth. However, it is surprising to find that there have been no efforts to bring together a comprehensive review and comparative analysis on these previous research endeavors, and some general principles and guidelines of engineering the perovskites toward advanced X-ray detectors have yet to be creamed off. Here, recent advances in engineering perovskites for direct X-ray detection are reviewed in the hope of providing fundamental understanding of this fast-developing field. First, the operation principles of direct X-ray detectors targeting flat-panel X-ray imaging will be introduced, particularly relevant to perovskite materials. Then, recent innovative works regarding the preparation and manipulation of single-crystalline and poly-crystalline perovskites are discussed in detail, through which specific effects of the intrinsic properties of the perovskite upon X-ray detection are highlighted. This is followed by a summary of the review and outlook of future directions.

In this paper, two novel D‐π‐D hole‐transporting materials (HTM) are reported, abbreviated as BDT‐PTZ and BDT‐POZ, which consist of 4,8‐di(hexylthio)‐benzo[1,2‐b:4,5‐b′]dithiophene (BDT) as π‐conjugated linker, and N‐(6‐bromohexyl) phenothiazine (PTZ)/N‐(6‐bromohexyl) phenoxazine (POZ) as donor units. The above two HTMs are deployed in p‐i‐n perovskite solar cells (PSCs) as dopant‐free HT layers, exhibiting excellent power conversion efficiencies of 18.26% and 19.16%, respectively. Particularly, BDT‐POZ demonstrates a superior fill factor of 81.7%, which is consistent with its more efficient hole extraction and transport verified via steady‐state/transient fluorescence spectra and space‐charge‐limited current technique. Single‐crystal X‐ray diffraction characterization implies these two molecules present diverse packing tendencies, which may account for various interfacial hole‐transport ability in PSCs.