No abstract

Cs4PbBr6 perovskites have attracted much attention recently due to their outstanding optical properties including efficient and narrowband green emission and unexpected high exciton binding energy. In this work, the exciton recombination behaviors in solution-grown Cs4PbBr6 single crystals were investigated via temperature-dependent photoluminescence (PL) spectroscopy in the temperature range of 83–293 K. X-ray diffraction as well as room-temperature PL and absorption investigations suggested that the efficient green emission was attributed to the parasitic CsPbBr3 nanocrystals embedded in the Cs4PbBr6 host matrix. With increasing temperature, the PL spectrum blueshifted and broadened monotonously. In addition, thermal quenching and antiquenching behaviors of PL emission were observed, which involves exciton trapping by CsPbBr3 nanocrystal surface defect states, exciton dissociation, and delocalization of excitons localized at CsPbBr3/Cs4PbBr6 interface states. Accordingly, a schematic model was finally proposed. The results reported in this paper will provide valuable insights into the origination of efficient green emission observed in Cs4PbBr6 perovskites.

In this work, we have reported self-powered narrowband visible-light photodetectors based on organolead halide perovskite CH3NH3PbBr3 (MAPbBr3)/p-Si heterojunctions, which were prepared by growing MAPbBr3 microcrystals on the p-Si substrate using a room-temperature antisolvent-assisted crystallization method. Morphological, structural, and optical investigations showed that the as-grown MAPbBr3 microcrystals possessed a high crystalline quality. Electrical characterizations showed that the hetero-pn junction was formed within the MAPbBr3/p-Si heterojunction. Thanks to the high crystalline quality of MAPbBr3 microcrystals, the as-fabricated heterojunction photodetectors operating under a bias voltage of 0 V exhibited a high on–off ratio of ∼5.3 × 105, a narrow photosensitivity spectrum with the full width at half maximum of 18.2 nm, a high photoresponse speed with the rising/falling time of 115.7/53.4 ms, and excellent stability to visible-light signals. Finally, the photodetection mechanism was proposed. It showed that the observed narrowband photodetection was attributed to the self-filtering effect caused by the thick MAPbBr3 microcrystals. The results presented in this work will provide valuable strategies for the fabrication of self-powered narrowband visible-light photodetectors in the future.

Owing to the intense carrier recombination and limited optical absorption, the as‐fabricated CsPbBr3 visible light photodetectors (PDs) are far from practical application. In this work, we have demonstrated performance‐improved metal‐semiconductor‐metal (MSM) structured CsPbBr3 visible light PDs realized by the decoration of sputtered Au nanoparticles (NPs). It showed that the Au NPs on the CsPbBr3 exhibited synergistic benefits including improving the photogenerated charge carriers’ lifetime and enhancing the optical absorption of the CsPbBr3, both of which are fundamental factors for the performance‐improved PDs. Electrical characterizations showed that localized Schottky junctions formed at the Au NPs/CsPbBr3 interface. In addition, optical investigations showed that effective resonant coupling occurred between the localized surface plasmon resonance effects of Au NPs and excitons in the CsPbBr3. As a result, the on‐off switching of the Au‐decorated CsPbBr3 photodetector increased by 13 times compared with that of the pristine one. Meanwhile, the peak photo sensitivity of the CsPbBr3 photodetector was increased from 0.088 to 0.61 A W‐1 after the decoration of Au NPs. It is believed that the results shown in this work will provide pathways for fabricating high‐performance CsPbBr3 PDs and other similar devices in the future.

Semiconductor heterojunctions consisting of lead halide perovskite (LHP) and silicon materials are important candidates for the fabrication of self‐powered visible‐light photodetectors. However, the interface recombination caused by interface trap states greatly deteriorates the performance of self‐powered photodetection, but fortunately, it can be suppressed by interfacial engineering. In this work, self‐powered narrowband visible‐light photodetection is demonstrated in the LHP CH3NH3PbBr3/p‐Si heterojunctions. Notably, the self‐powered photodetection performance is greatly enhanced by introducing an atomic‐layer‐deposition‐grown amorphous Al2O3 thin interlayer. Electrical and optical properties measurements suggest that the Al2O3 thin interlayer effectively passivates (reduces) the heterojunction interface trap states. On this basis, the CH3NH3PbBr3/Al2O3/p‐Si heterojunctions exhibit a decreased dark current and increased photocurrent simultaneously compared to CH3NH3PbBr3/p‐Si heterojunctions. Finally, a responsivity as high as 0.39 A W−1 and detectivity as high as 8.45 × 1012 Jones under the bias voltage of 0 V are obtained, which are higher than most reported state‐of‐the‐art devices. The results reported in this work will provide valuable pathways for the fabrication of high‐performance self‐powered narrowband photodetectors based on LHP/Si heterojunctions.