No abstract

Effective modification of the structure and properties of halide perovskites via the pressure engineering strategy has attracted enormous interest in the past decade. However, sufficient effort and insights regarding the potential properties and applications of the high-pressure amorphous phase are still lacking. Here, the superior and tunable photoelectric properties that occur in the pressure-induced amorphization process of the halide perovskite Cs 3 Bi 2 I 9 are demonstrated. With increasing pressure, the photocurrent with xenon lamp illumination exhibits a rapid increase and achieves an almost five orders of magnitude increment compared to its initial value. Impressively, a broadband photoresponse from 520 to 1650 nm with an optimal responsivity of 6.81 mA W −1 and fast response times of 95/96 ms at 1650 nm is achieved upon successive compression. The high-gain, fast, broadband, and dramatically enhanced photoresponse properties of Cs 3 Bi 2 I 9 are the result of comprehensive photoconductive and photothermoelectric mechanisms, which are associated with enhanced orbital coupling caused by an increase in Bi-I interactions in the [BiI 6 ] 3− cluster, even in the amorphous state. These findings provide new insights for further exploring the potential properties and applications of amorphous perovskites.

Photoelectric devices based on the photothermoelectric (PTE) effect show promising prospects for broadband detection without an external power supply. However, effective strategies are still required to regulate the conversion efficiency of light to heat and electricity. Herein, significantly enhanced photoresponse properties of PbI2 generated from a PTE mechanism via a high‐pressure strategy are reported. PbI2 exhibits a stable, fast, self‐driven, and broadband photoresponse at ≈980 nm. Intriguingly, the synergy of the photoconductivity and PTE mechanism is conducive to enhancing the photoelectric properties, and extending the detection bandwidth to the optical communication waveband (1650 nm) with an external bias. The dramatically enhanced photoresponse characteristics are attributed to narrowing of the band gap and a significantly decreased resistance, which originate from the enhancement of atomic orbital overlap owing to pressure‐induced Pb‐I bond contraction. These findings open up a new avenue toward designing self‐driven and broadband photoelectric devices.

Quaternary layered transition metal thiophosphate CuInP2S6 (CIPS) has attracted extensive research interest because of its outstanding optical and ferroelectric properties. Pressure-tuned phase transition is an efficient method to regulate the properties of functional materials in situ, yet there is still much to explore. Herein, we studied the pressure-regulated optoelectronic properties of CIPS and found a four-stage evolution of photoresponsivity under compression. The photoresponse of CIPS barely changes with pressure initially but increases dramatically above 4.2 GPa. Under further compression, the photoresponse first shows a decrease above 7.5 GPa and then a significant increase up to 23.5 GPa. Remarkably, the photoresponse at the highest pressure enhances by two orders of magnitude compared with the starting value. To investigate the origin of these abnormal variations in CIPS, high-pressure UV–vis absorption, Raman, and XRD measurements were conducted and a phase transition from Cc to P3̅1m symmetry was found at approximately 4.0 GPa. We suggest that the pressure-modulated optoelectronic properties in CIPS are closely related to the conductivity change of CIPS caused by its structural phase transition. Our study spotlights the outstanding pressure regulation of optoelectronic properties in CIPS, which paves the way for modifying the behavior of other optoelectronic materials.