The technological evolution has been progressing for centuries and will possibly increase at a higher rate in the 21st century. Currently, in this age of nanotechnology, the discovery of more economical and sustainable novel materials has considerably increased. The abundance of two-dimensional (2D) materials has endowed them with a broad material platform in technical studies and in the expansion of nano- and atomic-level applications. The innovation of graphene has motivated considerable attention to the study of other novel 2D materials, known as modern day “alchemy”, by which scientists are trying to convert most possible periodic table elements into 2D material structures and forms. 2D material devices with high quality and good optical encoder performance have a multitude of industrial applications. However, their stability and large size restrict their applications, but these problems can be overcome by functionalization and substrate-based formation of 2D materials. Therefore, via this review, first, basic attributes of 2D materials are described, and the mechanisms to further enhance their properties are also summarized. Second, the applications of 2D materials are discussed, along with their advantages and disadvantages. Finally, some effective device-fabrication approaches, such as heterostructure approaches, are applied to further enhance the properties of 2D materials; their novel device applications and opportunities are also presented. This updated review may provide new avenues for 2D material synthesis and development of more efficient devices compared to conventional devices in different fields.

Recent developments in emerging two-dimensional materials and their applications

Perovskite photodetectors (PPDs), which combine the advantages of perovskite semiconductor materials with superior optical and electronic properties and solution-processed manufacturing, have emerged as a new class of revolutionary optoelectronic devices with potential for various practical applications. Encouraged by the development of various solution-synthesis and film-deposition techniques for controlling the morphology and composition of perovskite materials with interesting optoelectronic properties, increasing research attention is focused on the development of high performance PPDs. In this review, the recent progress on emerging PPDs is comprehensively summarized from the perspective of device physics and materials science. The strategies for extending the spectral response range of PPDs and improving the performance of devices are investigated. Furthermore, the methods for realizing narrowband photodetectors are also discussed, where filter-free and self-filter narrowband PPDs are achieved based on the concept of charge collection narrowing. Meanwhile, the promising future directions in this research field are proposed and discussed, including multifunctional PPDs, perovskite–organic hybrid photodetectors, flexible and transparent PPDs, self-powered PPDs, and photodetector systems and arrays. This review provides valuable insights into the current status of highly sensitive PPDs and will spur the design of new structures and devices to further enhance their photo-detection performances and meet the need of versatility in practical application.

Recent progress on highly sensitive perovskite photodetectors

This work shows the large‐area growth of high‐quality vertically aligned PtSe 2 , and its application to photodetectors based on PtSe 2 ‐GaAs heterojunctions which exhibit a broadband sensitivity to illumination ranging from deep ultraviolet to near‐infrared light, with a peak sensitivity in the region from 650 to 810 nm. The high‐performance broadband photodetector will develop the next‐generation 2D Group‐10 materials based optoelectronic devices.

Fast, Self-Driven, Air-Stable, and Broadband Photodetector Based on Vertically Aligned PtSe2/GaAs Heterojunction

Due to its significant applications in many relevant fields, light detection in the solar-blind deep-ultraviolet (DUV) wavelength region is a subject of great interest for both scientific and industrial communities. The rapid advances in preparing high-quality ultrawide-bandgap (UWBG) semiconductors have enabled the realization of various high-performance DUV photodetectors (DUVPDs) with different geometries, which provide an avenue for circumventing numerous disadvantages in traditional DUV detectors. This article presents a comprehensive review of the applications of inorganic UWBG semiconductors for solar-blind DUV light detection in the past several decades. Different kinds of DUVPDs, which are based on varied UWBG semiconductors including Ga2O3, MgxZn1−xO, III-nitride compounds (AlxGa1−xN/AlN and BN), diamond, etc., and operate on different working principles, are introduced and discussed systematically. Some emerging techniques to optimize device performance are addressed as well. Finally, the existing techniques are summarized and future challenges are proposed in order to shed light on development in this critical research field.

Recent Progress in Solar-Blind Deep-Ultraviolet Photodetectors Based on Inorganic Ultrawide Bandgap Semiconductors

Solar-blind photodetectors are of great interest to a wide range of industrial, civil, environmental, and biological applications. As one of the emerging ultrawide-bandgap semiconductors, gallium oxide (Ga2O3) exhibits unique advantages over other wide-bandgap semiconductors, especially in developing high-performance solar-blind photodetectors. This paper comprehensively reviews the latest progresses of solar-blind photodetectors based on Ga2O3 materials in various forms of bulk single crystal, epitaxial films, nanostructures, and their ternary alloys. The basic working principles of photodetectors and the fundamental properties and synthesis of Ga2O3, as well as device processing developments, have been briefly summarized. A special focus is to address the physical mechanism for commonly observed huge photoconductive gains. Benefitting from the rapid development in material epitaxy and device processes, Ga2O3-based solar-blind detectors represent to date one of the most prospective solutions for UV detection technology towards versatile applications.

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Review of gallium-oxide-based solar-blind ultraviolet photodetectors

A deep UV light photodetector is assembled by coating multilayer graphene on beta-gallium oxide (β-Ga2 O3 ) wafer. Optoelectronic analysis reveals that the heterojunction device is virtually blind to light illumination with wavelength longer than 280 nm, but is highly sensitive to 254 nm light with very good stability and reproducibility.

Graphene-β-Ga2O3 Heterojunction for Highly Sensitive Deep UV Photodetector Application

In this study, we developed a sensitive red-light photodetector (RLPD) based on CsBi3I10 perovskite thin film This inorganic, lead-free perovskite was fabricated by a simple spin-coating method Device analysis reveals that the as-assembled RLPD was very sensitive to 650 nm light, with an on/off ratio as high as 105 The responsivity and specific detectivity of the device were estimated to be 218 A/W and 193 × 1013 Jones, respectively, which are much better than those of other lead halide perovskite devices In addition, the device shows a fast response (rise time: 033 ms; fall time: 038 ms) and a high external quantum efficiency (413 × 103%) It is also revealed that the RLPD has a very good device stability even after storage for 3 months under ambient conditions In summary, we suggest that the CsBi3I10 perovskite photodetector developed in this study may have potential applications in future optoelectronic systems

High-Performance Red-Light Photodetector Based on Lead-Free Bismuth Halide Perovskite Film.

In this study, we present a broadband nano-photodetector based on single-layer graphene (SLG)-carbon nanotube thin film (CNTF) Schottky junction. It was found that the as-fabricated device exhibited obvious sensitivity to a wide range of illumination, with peak sensitivity at 600 and 920 nm. In addition, the SLG-CNTF device had a fast response speed (τr = 68 μs, τf = 78 μs) and good reproducibility in a wide range of switching frequencies (50-5400 Hz). The on-off ratio, responsivity, and detectivity of the device were estimated to be 1 × 102, 209 mAW-1 and 4.87 × 1010 cm Hz1/2 W-1, respectively. What is more, other device parameters including linear performance θ and linear dynamic range (LDR) were calculated to be 0.99 and 58.8 dB, respectively, which were relatively better than other carbon nanotube based devices. The totality of the above study signifies that the present SLG-CNTF Schottky junction broadband nano-photodetector may have promising application in future nano-optoelectronic devices and systems.

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Broadband photodetector based on carbon nanotube thin film/single layer graphene Schottky junction.

ZIF-67 derived porous Co3O4 hollow nanopolyhedron functionalized solution-gated graphene transistors for simultaneous detection of glucose and uric acid in tears.

A highly sensitive ultraviolet A (UVA) and violet photodetector based on p-type single-layer graphene (SLG)-TiO2 heterostructure was fabricated by transferring chemical vapor deposition derived SLG on the surface of commercial single-crystal TiO2 wafer Optoelectronic analysis reveals the as-fabricated Schottky junction PD was highly sensitive to light illumination in UVA and violet range, with peak sensitivity at 410 nm and excellent stability and reproducibility, but virtually blind to illumination with wavelength less than 350 nm or more than 460 nm The on/off ratio of the device was calculated to be 68 × 104, which is better than the majority of previously reported TiO2 based PDs What is more, the rise/fall time were estimated to be 074/118 ms, much faster than other TiO2 based counterparts The totality of the above result signifies that the present SLG-TiO2 Schottky junction photodetector may have promising application in future high-speed, high-sensitivity optoelectronic nanodevices and systems

Wei-Yu Kong

Papers

Graphene-β-Ga2O3 Heterojunction for Highly Sensitive Deep UV Photodetector Application

High-Performance Red-Light Photodetector Based on Lead-Free Bismuth Halide Perovskite Film.

Broadband photodetector based on carbon nanotube thin film/single layer graphene Schottky junction.

ZIF-67 derived porous Co3O4 hollow nanopolyhedron functionalized solution-gated graphene transistors for simultaneous detection of glucose and uric acid in tears.

Highly sensitive UVA and violet photodetector based on single-layer graphene-TiO 2 heterojunction.