Template-Assisted Synthesis of 2D Perovskite Grating Single Crystal Films at Low Temperatures for UV Polarization-Sensitive Photodetectors.

2D perovskites have attracted tremendous attention due to their superior optoelectronic properties and potential applications in optoelectronic devices. Especially, the larger bandgap of 2D perovskite means that they are suitable for UV photodetection. However, the layered structure of 2D perovskites hinders the interlayer carrier transport, which limits the improvement of device performance. Therefore, nanoscale structures are normally used to enhance the light absorption ability, which is an effective strategy to improve the photocurrent in 2D perovskite-based photodetectors. Herein, a template-assisted low-temperature method is proposed to fabricate 2D perovskite ((C6H5C2H4NH3)2PbBr4, (PEA)2PbBr4) grating single crystal films (GSCFs). The crystallinity of the (PEA)2PbBr4 GSCFs is significantly improved due to the slow evaporation of the precursor solution under low temperatures. Based on this high crystalline quality and extremely ordered microstructures, the metal-semiconductor-metal photodetectors are assembled. Finite-different time-domain (FDTD) simulation and experiment indicate that the GSCF-based photodetectors exhibit significantly improved performance in comparison with the plane devices. The optimized 2D perovskite photodetectors are sensitive to UV light and demonstrate a responsivity and detectivity of 28.6 mA W-1 and 2.4 × 1011 Jones, respectively. Interestingly, the photocurrent of this photodetector varies as the angle of the incident polarized light, resulting in a high polarization ratio of 1.12.

Surface Microstructure Engineering in MAPbBr3 Microsheets for Performance-Enhanced Photodetectors.

Metal halide-perovskite-based photodetectors have recently emerged as a class of promising optoelectronic devices in various fields. Meanwhile, nano/microstructuring perovskite-based photodetectors are a facile integration with complementary metal-oxide semiconductors for miniaturized imaging systems. However, there are still challenges to be overcome in reducing the losses caused by light reflection on the surface of microstructural perovskites. In this work, surface microstructure engineering is employed in MAPbBr3 microsheets for reducing light reflection and improving light absorption, resulting in high-performance perovskite photodetectors. MAPbBr3 microsheets, which possess different surface morphologies of flat, upright hemisphere arrays and inverted hemisphere arrays (IHAs), are fabricated by a simple microstructure template-assisted space confinement process. The light absorption capacity of IHA MAPbBr3 is significantly higher than that of the other two structures. Hence, IHA photodetectors with excellent figures of merit, including low dark current, decent responsivity, and fast speed, are achieved. Furthermore, the noise of the IHA photodetectors is only ∼10-13 A/Hz, which results in the superior sensitivity for weak light detection with a specific detectivity up to 1011 Jones. Our results demonstrate that surface engineering is a simple, low-cost, yet effective approach to improve the performance of nano-/micro-optoelectronic devices.