Hot-carrier cooling processes of perovskite materials are typically described by a single parabolic band model that includes the effects of carrier-phonon scattering, hot phonon bottleneck, and Auger heating. However, little is known (if anything) about the cooling processes in which the spin-degenerate parabolic band splits into two spin-polarized bands, i.e., the Rashba band splitting effect. Here, we investigated the hot-carrier cooling processes for two slightly different compositions of two-dimensional Dion–Jacobson hybrid perovskites, namely, (3AMP)PbI4 and (4AMP)PbI4 (3AMP = 3-(aminomethyl)piperidinium; 4AMP = 4-(aminomethyl)piperidinium), using a combination of ultrafast transient absorption spectroscopy and first-principles calculations. In (4AMP)PbI4, upon Rashba band splitting, the spin-dependent scattering of hot electrons is responsible for accelerating hot-carrier cooling at longer delays. Importantly, the hot-carrier cooling of (4AMP)PbI4 can be extended by manipulating the spin state of the hot carriers. Our findings suggest a new approach for prolonging hot-carrier cooling in hybrid perovskites, which is conducive to further improving the performance of hot-carrier-based optoelectronic and spintronic devices.
in a wide range of industrial applications, such as homeland security, medical diagnostics, food curing, sanitation, chemical and biological threat detection, space-tospace communications, missile detection, military surveillance, target detection and acquisition, transparent thin-film transistors, solar cells, white lighting, sterilization, medical treatment, and touch display panels. [1][2][3][4][5][6][7] For example, the most commercial DUV photodetectors are produced using UV-enhanced narrow bandgap semiconductors, mainly Si-based photodetector. [8,9] However, the narrow bandgap materials are ineffective in rejecting signals in the UV−vis−IR spectral region, making them unsuitable for DUV applications. Thus, high-quality DUV WBGSs are still needed to produce high-performance DUV optoelectronic devices. In each of the aforementioned fields, scientists and industry practitioners are looking to overcome different challenges. There is a growing demand for both p-type and n-type WBGSs that possess good stability and conductivity. The main obstacle to the achievement of this goal stems from the lack of p-type wide bandgap materials operating in the DUV range below 300 nm (i.e., >4.1 eV) that exhibit good p-type stability. Currently, the p-type materials having bandgap in the UV-A range (such as p-type GaN, Cu 2 O, and SnO) are utilized in DUV optoelectronics, which severely downgrade device performance, as their bandgaps are limited to the UV-A-to-visible spectral region (320-400 nm). [10,11] Moreover, though n-type WBGSs (e.g., ZnO, Ga 2 O 3 , and AlGaN) with good conductivity and stability can operate in the UV and DUV range (280−390 nm), it is not possible to convert them to a p-type material with good stability and conductivity due to their intrinsic electronic properties. [2,6,[11][12][13][14][15][16] Consequently, no highly stable conductive p-type DUV WBGS operating in both UV-B and UV-C region presently exists. [17] Further advances in the field of DUV optoelectronics are hindered by other issues, such as the difficulty in developing new cost-effective material production and fabrication methods that could replace the expensive and high vacuum-based technologies presently in use. Thus, as DUV-WBGS based devices tend Wide bandgap semiconductor (WBGS)-based deep UV (DUV) devices lag behind those operating in the visible and IR range, as no stable p-type WBGS that operates in the DUV region (<300 nm) presently exists. Here, solutionprocessed p-type manganese oxide WBGS quantum dots (MnO QDs) are explored. Highly crystalline MnO QDs are synthesized via femtosecond-laser ablation in liquid. The p-type nature of these QDs is demonstrated by Kelvin probe and field effect transistor measurements, along with density functional theory calculations. As proof of concept, a high-performance, self-powered, and solar-blind Schottky DUV photodetector based on such QDs is fabricated, which is capable of detecting under ambient conditions. The carrier collection efficiency is enhanced by asymmetric electrode structure, leadi...
A highly crystalline single-or few-layered 2D-MoS 2 induces a high dark current, due to which an extremely small photocurrent generated by a few photons can be veiled or distorted. In this report, we show that suppression in the dark current with the enhancement in the photocurrent of a 2D-based photodetector, which is a prerequisite for photoresponse enhancement, can be achieved by constructing an ideal p-n junction based on functionalizing n-type 2D-MoS 2 with p-type quantum dots (QDs). Highly crystalline solution-processed manganese oxide QDs (MnO QDs) are synthesized via the pulsed femtosecond laser ablation technique in ethanol. The ablated MnO QDs are spray-coated on an exfoliated 2D-MoS 2 substrate with interdigitated Au electrodes through N 2 -assisted spraying. In the resulting MnO QD-decorated 2D-MoS 2 photodetector with a heterojunction, dark current is reduced and is accompanied by photocurrent enhancement, thereby markedly improving the photoresponsivity and detectivity of MoS 2 -based devices. To elucidate the underlying mechanisms contributing to this enhancement, power-and wavelength-dependent photoresponses, along with material characterizations based on spectroscopic, chemical, morphological measurements, and analyses, are discussed.
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