Pressure-Tuning Photothermal Synergy to Optimize the Photoelectronic Properties in Amorphous Halide Perovskite Cs3 Bi2 I9

Efficient Carrier Transport in 2D Bi2O2Se/CsBi3I10 Perovskite Heterojunction Enables Highly-Sensitive Broadband Photodetection

2D Bi2O2Se has recently garnered significant attention in the electronics and optoelectronics fields due to its remarkable photosensitivity, broad spectral absorption, and excellent long-term environmental stability. However, the development of integrated Bi2O2Se photodetector with high performance and low-power consumption is limited by material synthesis method and the inherent high carrier concentration of Bi2O2Se. Here, a type-I heterojunction is presented, comprising 2D Bi2O2Se and lead-free bismuth perovskite CsBi3I10, for fast response and broadband detection. Through effective charge transfer and strong coupling effect at the interfaces of Bi2O2Se and CsBi3I10, the response time is accelerated to 4.1 µs, and the detection range is expanded from ultraviolet to near-infrared spectral regions (365-1500 nm). The as-fabricated photodetector exhibits a responsivity of 48.63 AW-1 and a detectivity of 1.22×1012 Jones at 808 nm. Moreover, efficient modulation of the dominant photocurrent generation mechanism from photoconductive to photogating effect leads to sensitive response exceeding 103 AW-1 for heterojunction-based photo field effect transistor (photo-FETs). Utilizing the large-scale growth of both Bi2O2Se and CsBi3I10, the as-fabricated integrated photodetector array demonstrates outstanding homogeneity and stability of photo-response performance. The proposed 2D Bi2O2Se/CsBi3I10 perovskite heterojunction holds promising prospects for the future-generation photodetector arrays and integrated optoelectronic systems.

Pressure-Driven Polymorphic Transition, Emergent Insulator-To-Metal Transition, and Photoconductivity Switching in Violet Phosphorus

Polymorphic phase transition is an essential phenomenon in condensed matter that the physical properties of materials may undergo significant changes due to the structural transformation. Phase transition has thus become an important means and dimension for regulating material properties. Herein, this study demonstrates the pressure-induced multi-transition of both structure and physical properties in violet phosphorus, a novel phosphorus allotrope. Under compression, violet phosphorus undergoes sequential polymorphic phase transitions. Concomitant with the first phase transition, violet phosphorus exhibits emergent insulator-metal transition, superconductivity, and dramatic switching from positive to negative photoconductivity. Remarkably, the resistance of violet phosphorus shows a sudden drop of around 107 along with the phase transition. In addition, piezochromism from translucent red to opaque black and suppression of photoluminescence are observed upon compression. Of particular interest is that the sample irreversibly transforms into black phosphorus with a pronounced discrepancy in physical properties from the pristine violet phosphorus after decompression. The abundant polymorphic transitions and property changes in violet phosphorus have significant implications for designing novel pressure-responsive electronic/optoelectronic devices and exploring concealed polymorphic transition materials.

Tailoring the high-brightness "warm" white light emission of two-dimensional perovskite crystals via a pressure-inhibited nonradiative transition

Efficient warm white light emission is an ideal characteristic of single-component materials for light-emitting applications. Although two-dimensional hybrid perovskites are promising candidates for light-emitting diodes, as they possess broadband self-trapped emission and outstanding stability, they rarely achieve a high photoluminescence quantum yield of warm white light emissions. Here, an unusual pressure-induced warm white emission enhancement phenomenon from 2.1 GPa to 9.9 GPa was observed in two-dimensional perovskite (2meptH2)PbCl4, accompanied by a large increase in the relative quantum yield of photoluminescence. The octahedral distortions, accompanied with the evolution of organic cations, triggered the structural collapse, which caused the sudden emission enhancement at 2.1 GPa. Afterwards, the further intra-octahedral collapse promotes the formation of self-trapped excitons and the substantial suppression of nonradiative transitions are responsible for the continuous pressure-induced photoluminescence enhancement. This study not only clearly illustrates the relationship between crystal structure and photoluminescence, but also provides an experimental basis for the synthesis of high-quality warm white light-emitting 2D metal halide perovskite materials.