Photoelectric detectors are the central part of modern photodetection systems with numerous commercial and scientific applications. p‐Type semiconductor materials play important roles in ...optoelectronic devices. Photodetectors based on p‐type semiconductor materials have attracted a great deal of attention in recent years because of their unique properties. Here, a comprehensive summary of the recent progress mainly on photodetectors based on inorganic p‐type semiconductor materials is presented. Various structures, including photoconductors, phototransistors, homojunctions, heterojunctions, p–i–n junctions, and metal–semiconductor junctions of photodetectors based on inorganic p‐type semiconductor materials, are discussed and summarized. Perspectives and an outlook, highlighting the promising future directions of this research field, are also given.
Aside from n‐type semiconductors, p‐type semiconductor materials also play important roles in photoelectric detectors. After carefully referring to related literature, a comprehensive review of recent progress mainly on various inorganic p‐type semiconductor‐material‐based photodetectors with diverse structures is presented, including photoconductive‐type, phototransistor‐type, p–n hybrid structures, and metal–semiconductor junctions.
BiOCl nanosheets/TiO2 nanotube arrays heterojunction UV photodetector (PD) with high performance is fabricated by a facile anodization process and an impregnation method. The heterojunction at the ...interface and the internal electric fields in the BiOCl nanosheets faciliate the separation of photogenerated charge carriers and regulate the transportation of the electrons. Compared with the large dark current (≈10−5 A), low on/off ratio (8.5), and slow decay time (>60 s) of the TiO2 PD, the optimized heterojunction PD (6‐BiOCl–TiO2) yields dramatically decreased dark current (≈1 nA), ultrahigh on/off ratio (up to 2.2 × 105), and fast decay speed (0.81 s) under 350 nm light illumination at −5 V. Moreover, it exhibits an increased responsivity of 41.94 A W−1, a remarkable detectivity (D*) of 1.41 × 1014 Jones, and a high linear dynamic range of 103.59 dB. The loading amount and growth orientations of the BiOCl nanosheets alter the roles of the self‐induced internal electric field in regulating the behaviors of the charge carriers, thus affecting the photoelectric properties of the heterojunction PDs. These results demonstrate that rational construction of novel heterojunctions hold great potentials for fabricating photodetectors with high performance.
A BiOCl–TiO2 heterojunction UV photodetector with high performance is fabricated. Heterojunctions formed between BiOCl nanosheets and TiO2 nanotube arrays improve the UV photoresponses and response speed of TiO2 film photodetectors. The loading amount and growth orientation of BiOCl nanosheets on the TiO2 film have great influences on the photoelectric performance of the heterojunction photodetector.
2D perovskites, due to their unique properties and reduced dimension, are promising candidates for future optoelectronic devices. However, the development of stable and nontoxic 2D wide‐bandgap ...perovskites remains a challenge. 2D all‐inorganic perovskite Sr2Nb3O10 (SNO) nanosheets with thicknesses down to 1.8 nm are synthesized by liquid exfoliation, and for the first time, UV photodetectors (PDs) based on individual few‐layer SNO sheets are investigated. The SNO sheet‐based PDs exhibit excellent UV detecting performance (narrowband responsivity = 1214 A W−1, external quantum efficiency = 5.6 × 105%, detectivity = 1.4 × 1014 Jones @270 nm, 1 V bias), and fast response speed (trise ≈ 0.4 ms, tdecay ≈ 40 ms), outperforming most reported individual 2D sheet‐based UV PDs. Furthermore, the carrier transport properties of SNO and the performance of SNO‐based phototransistors are successfully controlled by gate voltage. More intriguingly, the photodetecting performance and carrier transport properties of SNO sheets are dependent on their thickness. In addition, flexible and transparent PDs with high mechanical stability are easily fabricated based on SNO nanosheet film. This work sheds light on the development of high‐performance optoelectronics based on low‐dimensional wide‐bandgap perovskites in the future.
Liquid‐exfoliated 2D wide‐bandgap perovskite Sr2Nb3O10 (SNO) nanosheets are explored for high‐performance UV photodetection. Phototransistors based on individual few‐layer SNO nanosheets exhibit outstanding, narrowband, and thickness‐dependent photoresponsivity as high as 1214 A W−1 and fast response speed. Flexible, transparent photodetectors with high mechanical stability are easily fabricated based on SNO nanosheet film.
Developing efficient and affordable catalysts is of great significance for energy and environmental sustainability. Heterostructure photocatalysts exhibit a better performance than either of the ...parent phases as it changes the band bending at the interfaces and provides a driving force for carrier separation, thus mitigating the effects of carrier recombination and back‐reaction. Herein, the photo/electrochemical applications of a variety of metal sulfides (MSx) (MoS2, CdS, CuS, PbS, SnS2, ZnS, Ag2S, Bi2S3, and In2S3)/TiO2 heterojunctions are summarized, including organic degradation, water splitting, and CO2 reduction conversion. First, a general introduction on each MSx material (especially bandgap structures) will be given. Then the photo/electrochemical applications based on MSx/TiO2 heterostructures are reviewed from the perspective of light harvesting ability, charge carrier separation and transportation, and surface chemical reactions. Special focus is given to CdS/TiO2 and PbS/TiO2‐based quantum dot sensitized solar cells. Ternary composites by taking advantages of positive synergetic effects are also well summarized. Finally, conclusions are made regarding approaches for structure design, and the authors' perspective on future architectural design and electrode construction is given. This work will make up the gap for TiO2 nanocomposites and shed light on the fabrication of more efficient MSx‐metal oxide junctions in photo/electrochemical applications.
Structure steering of MSx/TiO2 heterojunctions in photodegradation, water splitting, and CO2 conversion are reviewed herein, mainly focusing on improved light harvesting, effective interfacial charge transfer, and affordable active sites for surface chemical reactions. Special focus is given to the quantum dot sensitized solar cells.
A novel self‐powered UV photodetector based on electrospun ZnO nanofiber arrays is introduced. Aligned pure ZnO nanofibers and Ag‐doped p‐type ZnO nanofibers are processed perpendicular to each ...other, and p–n junction arrays of ZnO nanofibers are fabricated as a result. Owing to the intrinsic intervals between nanofibers, the device is fully transparent on quartz substrate. Various characterization methods including TEM, XRD, and XPS are used to testify the existence form of Ag element in ZnO nanofibers, and a field effect transistor is constructed to judge their conductivity. It is discovered that the Ag doping process not only transforms ZnO to p‐type conductivity, making it possible to build this self‐powered photodetector, but also forms Ag nanoparticles in ZnO nanofibers and thus helps reduce the response time. Benefiting from the abovementioned dual effects, this UV detector is found to have an enhanced performance, with the on–off ratio up to 104 at zero bias and a rather short rise/decay time of 3.90 s/4.71 s.
A novel transparent and self‐powered UV photodetector based on crossed ZnO nanofiber array homojunction is fabricated by partially Ag‐doping in electrospinning process, which exhibits high on–off ratio and fast response. The Ag‐doping not only transforms ZnO to p‐type conductivity to build p–n junction, but also forms Ag nanoparticles inside ZnO nanofibers to build internal Schottky barriers and reduce response time.
Uniformly aligned electrospun nanofiber arrays are important building blocks for high-performance functional devices and device arrays. However, it remains a challenge to prepare perfectly aligned ...and large area nanofiber arrays using common electrospinning. In this work, a modified electrospinning method utilizing three assisted electrodes for nanofiber collection was proposed to achieve uniformly aligned and millimeter-long ZnO and NiO nanofiber arrays (more than 90% of nanofibers aligned to within ±4° of the desired direction), which were further fabricated into ZnO/NiO heterojunction arrays with a density of 10 6 cm −2 . Photodetectors (PDs) based on the as-prepared ZnO/NiO heterojunction arrays exhibited excellent ultraviolet (UV) selective and self-powered detection properties because of the properly matched energy bands of ZnO and NiO. A maximum responsivity of 0.415 mA W −1 and a short rise/decay time of 7.5 s/4.8 s at 0 V bias of the device markedly outstripped the reference ZnO nanofiber array device. The three-assisted-electrode electrospinning method of this work offers new chances in novel nanostructure design and high-performance device fabrication.
Inspired by nanoscience and nanoengineering, numerous nanostructured materials developed by multidisciplinary approaches exhibit excellent photoelectronic properties ranging from ultraviolet to ...terahertz frequencies. As a new class of building block, nanoscale elements in terms of quantum dots, nanowires, and nanolayers can be used for fabricating photodetectors with high performance. Moreover, in conjunction with traditional photodetectors, they exhibit appealing performance for practical applications including high density of integration, high sensitivity, fast response, and multifunction. Therefore, with the perspective of photodetectors constructed by diverse low‐dimensional nanostructured materials, recent advances in nanoscale photodetectors are discussed here; meanwhile, challenges and promising future directions in this research field are proposed.
Nanostructured materials with different dimensions, such as nanolayers, nanowires, and quantum dots, exhibit excellent photoelectronic properties for photodetectors ranging from the ultraviolet to terahertz frequencies. Besides excellent performances of high sensitivity and fast response for practical applications, they also exhibit many appealing features like high density of integration and multifunction, in conjunction with traditional photodetectors.
Ultraviolet photodetectors (UV PDs) with “5S” (high sensitivity, high signal‐to‐noise ratio, excellent spectrum selectivity, fast speed, and great stability) have been proposed as promising ...optoelectronics in recent years. To realize high‐performance UV PDs, heterojunctions are created to form a built‐in electrical field for suppressing recombination of photogenerated carriers and promoting collection efficiency. In this progress report, the fundamental components of heterojunctions including UV response semiconductors and other materials functionalized with unique effects are discussed. Then, strategies of building PDs with lattice‐matched heterojunctions, van der Waals heterostructures, and other heterojunctions are summarized. Finally, several applications based on heterojunction/heterostructure UV PDs are discussed, compromising flexible photodetectors, logic gates, and image sensors. This work draws an outline of diverse materials as well as basic assembly methods applied in heterojunction/heterostructure UV PDs, which will help to bring about new possibilities and call for more efforts to unleash the potential of heterojunctions.
Heterojunction UV photodetectors with high responsivity and fast speed are an essential part of optoelectronics. This article summarizes recently developed sensitive materials applied in heterojunction UV photodetectors and different integration methods including lattice matching and van der Waals integration, as well as other heterojunctions. Several representative applications are also reviewed to provide a comprehensive insight.
Self‐powered ultraviolet (UV) photodetectors, which have vast applications in the military and for civilian purposes, have become particularly attractive in recent years due to their advantages of ...high sensitivity, ultrasmall size, and low power consumption. In particular, self‐powered UV photodetectors driven by a built‐in electric field cannot only detect UV signals but also be powered by the incident signals instead of external power. In this concept, the key issues and most recent developments on photovoltaic type UV photodetectors driven by p–n homojunction, heterojunction, and Schottky junction are surveyed. This should generate extensive interest in this field and encourage more researchers to engage in and tackle the scientific challenges.
In this Concept, self‐powered UV photodetectors driven by a built‐in electric field are presented, which is extremely important for applications in UV detection. The key issues and developments of photovoltaic‐type UV photodetectors driven by the p–n homojunction, heterojunction, and Schottky junction are surveyed. Additionally, the development tendency of next generation photovoltaic‐type UV is also proposed.
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