An ultrahigh responsivity self-powered solar-blind photodetector based on a centimeter-sized β-Ga2O3/polyaniline heterojunction

Ultrasensitive Self-Powered Flexible Crystalline β-Ga2O3-Based Photodetector Obtained through Lattice Symmetry and Band Alignment Engineering

Due to its portable and self-powered characteristics, the construction of Ga2O3-based semiconductor flexible devices that can improve the adaptability in various complex environments have drawn great attention in recent decades. However, conventional Ga2O3-based flexible heterojunctions are based on either amorphous or poor crystalline Ga2O3 materials, which severely limit the performance of the corresponding devices. Here, through lattice-symmetry and energy-band alignment engineering, we construct a high-quality crystalline flexible NiO/β-Ga2O3 p-n self-powered photodetector. Owing to its suitable energy-band alignment structure, the device shows a high photo-to-dark current ratio (1.71 × 105) and a large detection sensitivity (6.36 × 1014 Jones) under zero bias, which is superior than most Ga2O3 self-powered photodetectors even for those based on rigid substrates. Moreover, the fabricated photodetectors further show excellent mechanical stability and robustness in bending conditions, demonstrating their potential practical applications in flexible optoelectronic devices. These findings provide insights into the manipulation of crystal lattice and energy band engineering in flexible self-powered photodetectors and also offer guideline for designing other Ga2O3-based flexible electronic devices.

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

Ultrawide bandgap (UWBG) semiconductors, including Ga2O3, diamond, Al x Ga1-x N/AlN, featuring bandgaps greater than 4.4 eV, hold significant promise for solar-blind ultraviolet photodetection, with applications spanning in environmental monitoring, chemical/biological analysis, industrial processes, and military technologies. Over recent decades, substantial strides in synthesizing high-quality UWBG semiconductors have facilitated the development of diverse high-performance solar-blind photodetectors (SBPDs). This review comprehensively examines recent advancements in UWBG semiconductor-based SBPDs across various device architectures, encompassing photoconductors, metal-semiconductor-metal photodetectors, Schottky photodiodes, p-n (p-i-n) photodiodes, phototransistors, etc., with a systematic introduction and discussion of their operational principles. The current state of device performance for SBPDs employing these UWBG semiconductors is evaluated across different device configurations. Finally, this review outlines key challenges to be addressed, aiming to steer future research endeavors in this critical domain.

Wide Bandgap Semiconductors for Ultraviolet Photodetectors: Approaches, Applications, and Prospects

Ultraviolet (UV) light, invisible to the human eye, possesses both benefits and risks. To harness its potential, UV photodetectors (PDs) have been engineered. These devices can convert UV photons into detectable signals, such as electrical impulses or visible light, enabling their application in diverse fields like environmental monitoring, healthcare, and aerospace. Wide bandgap semiconductors, with their high-efficiency UV light absorption and stable opto-electronic properties, stand out as ideal materials for UV PDs. This review comprehensively summarizes recent advancements in both traditional and emerging wide bandgap-based UV PDs, highlighting their roles in UV imaging, communication, and alarming. Moreover, it examines methods employed to enhance UV PD performance, delving into the advantages, challenges, and future research prospects in this area. By doing so, this review aims to spark innovation and guide the future development and application of UV PDs.

An investigation into the hybrid architecture of Mn-Co nanoferrites incorporated into a polyaniline matrix for photoresponse studies

In this study, an enhanced photoresponse was observed in the Mn-Co Nanoferrites (MCFs)-Polyaniline (PANI) nanohybrid architecture due to the formation of interface between PANI and MCFs, which provided a conduction pathway for the movement of charge carriers, and these interfaces were observed in a high-resolution transmission electron micrograph (HR-TEM). X-ray photoelectron spectroscopy (XPS) suggests that the carbon (C 1s) of the MCF-PANI nanohybrid shows peaks at 287.80 eV for CO, 286.17 eV for C-O, 285.24 eV for C-N, 284.50 eV for the sp3 hybridized carbon (C-C/C-H) and 283.84 eV for the sp2 hybridized carbon (CC). Current-voltage (I-V) curves reveal an ohmic nature of the MCF-PANI nanohybrid photodetector device. The photoresponse measurements were analyzed using the trap depth concept, demonstrating that the conductive polymer increases the photoconduction mechanism efficiency of MCFs. The constructed photodetector device exhibits a high photoresponsivity of 22.69 A W-1, a remarkable detectivity of 1.36 × 1012 cm Hz1/2 W-1 and a fast rise/decay time of 0.7/0.8 s. The excellent performance of the as-fabricated photodetector device could be explained by the intimate interaction between MCFs and PANI at their interface.

High-Performance Self-Driven Solar-Blind Ultraviolet Photodetectors Based on HfZrO2/β-Ga2O3 Heterojunctions

Ga₂O₃ is a wide-bandgap semiconductor that has shown great potential for application in solar-blind ultraviolet (UV) photodetectors. However, the responsivity and detectivity of Ga₂O₃-based self-driven solar-blind UV photodetectors are insufficient for practical applications at present because of the limited separation of photogenerated carriers in the devices. In this work, Hf_0.5Zr_0.5O₂/β-Ga₂O₃ heterojunction-based self-driven solar-blind UV photodetectors are constructed by combining ferroelectric Hf_0.5Zr_0.5O₂ (HfZrO₂) material with Ga₂O₃, taking advantage of the ultrawide bandgap of HfZrO₂ and the favorable II-type energy band configuration between both. Upon optimization, a HfZrO₂/β-Ga₂O₃ heterojunction-based UV photodetector with a HfZrO₂ layer thickness of 10 nm is shown to provide remarkable responsivity (R = (14.64 ± 0.3) mA/W) and detectivity (D* = (1.58 ± 0.03) × 10¹² Jones), which are much superior to those of a single Ga₂O₃-based device toward 240 nm light illumination. Further, the device performance is adjustable with varying poling states of HfZrO₂ and shows substantial enhancement in the upward poling state, benefiting from the constructive coupling of the ferroelectric depolarization electric field in HfZrO₂ and the built-in electric field at the HfZrO₂/β-Ga₂O₃ interface. Under illumination of weak light of 0.19 μW/cm², the upward poled device shows significantly enhanced R (52.6 mA/W) and D* (5.7 × 10¹² Jones) values. The performance of our device surpasses those of most previously reported Ga₂O₃-based self-driven photodetectors, indicating its great potential in practical applications for sensitive solar-blind UV detection.

Rapid Response Solar Blind Deep UV Photodetector with High Detectivity Based On Graphene:N/βGa2 O3 :N/GaN p-i-n Heterojunction Fabricated by a Reversed Substitution Growth Method

This work reports a high-detectivity solar-blind deep ultraviolet photodetector with a fast response speed, based on a nitrogen-doped graphene/βGa₂ O₃ /GaN p-i-n heterojunction. The i layer of βGa₂ O₃ with a Fermi level lower than the central level of the forbidden band of 0.2 eV is obtained by reversed substitution growth with oxygen replacing nitrogen in the GaN matrix, indicating the majority carrier is hole. X-ray diffractometershows that the transformation of GaN into βGa₂ O₃ with (-201) preferred orientation at temperature above 900 °C in an oxygen ambient. The heterojunction shows enhanced self-powered solar blind detection ability with a response time of 3.2 µs (rise)/0.02 ms (delay) and a detectivity exceeding 10¹² Jones. Under a reverse bias of -5 V, the photoresponsivity is 8.3 A W^-1 with a high I_light /I_dark ratio of over 10⁶ and a detectivity of ≈9 × 10¹⁴ Jones. The excellent performance of the device is attributed to 1) the continuous conduction band without a potential energy barrier, 2) the larger built-in potential in the heterojunction because of the downward shift of Fermi energy level in β-Ga₂ O₃ , and 3) an enhanced built-in electric field in the βGa₂ O₃ due to introducing p-type graphene with a high hole concentration of up to ≈10²⁰ cm^-3 .

Piezo-phototronic effect regulated broadband photoresponse of a-Ga2O3/ZnO heterojunction

Amorphous Ga₂O₃ (a-Ga₂O₃) films have attracted considerable attention in the field of photodetectors due to their excellent optical absorption response and photoelectric properties. However, there are few studies that have utilized the piezo-phototronic effect to regulate the broadband photoresponse of Ga₂O₃-based photodetectors. Here, a flexible a-Ga₂O₃/ZnO heterojunction was constructed, which demonstrated a broadband response range from deep ultraviolet (265 nm) to the near-infrared (1060 nm) and realized a bidirectional adjustable photocurrent response via the piezo-phototronic effect. Under 265 nm illumination and 0.5 V bias, the responsivity and detectivity of the a-Ga₂O₃/ZnO heterojunction reached up to 12.19 A W^-1 and 4.71 × 10¹¹ Jones under 0.164% compressive strain, corresponding to enhancements of 67.7% and 66.8% compared to those under a strain-free state, respectively. Moreover, the broadband photoresponse of the a-Ga₂O₃/ZnO heterojunction beyond the bandgap limit was tunable under bidirectional strain. The working mechanism of photoresponse performance for the a-Ga₂O₃/ZnO heterojunction at different wavelengths was elucidated in detail. Oxygen vacancy-assisted carrier generation was found to be influenced by the wavelength of incident light, which mainly determined the broadband photoresponse of the heterojunction. The modulation of the a-Ga₂O₃/ZnO heterojunction photodetector was interpreted in light of the strain-induced regulation of the barrier height. This work represents an important step toward the development of adjustable broadband photodetectors based on a-Ga₂O₃ films.

Ultrahigh Detectivity Broad Spectrum UV Photodetector with Rapid Response Speed Based on p-β Ga2 O3 /n-GaN Heterojunction Fabricated by a Reversed Substitution Doping Method

An excellent broad-spectrum (220-380 nm) UV photodetector, covering the UVA-UVC wavelength range, with an ultrahigh detectivity of ≈10¹⁵  cm Hz^1/2 W^-1 , is reported. It is based on a p-β Ga₂ O₃ /n-GaN heterojunction, in which p-β Ga₂ O₃ is synthesized by thermal oxidation of GaN and a heterostructure is constructed with the bottom n-GaN. XRD shows the oxide layer is (-201) preferred oriented β-phase Ga₂ O₃ films. SIMS and XPS indicate that the residual N atoms as dopants remain in β Ga₂ O₃ . XPS also demonstrates that the Fermi level is 0.2 eV lower than the central level of the band gap, indicating that the dominant carriers are holes and the β Ga₂ O₃ is p-type conductive. Under a bias of -5 V, the photoresponsivity is 56 and 22 A W^-1 for 255 and 360 nm, respectively. Correspondingly, the detectivities reach an ultrahigh value of 2.7 × 10¹⁵  cm Hz^1/2 W^-1 (255 nm) and 1.1 × 10¹⁵  cm Hz^1/2 W^-1 (360 nm). The high performance of this UV photodetector is attributed mainly to the continuous conduction band of the p-β Ga₂ O₃ /n-GaN heterojunction without a potential energy barrier, which is more helpful for photogenerated electron transport from the space charge region to the n-type GaN layer.

High-performance layer-structured Si/Ga2O3/CH3NH3PbI3 heterojunction photodetector based on a Ga2O3 buffer interlayer

Organic-inorganic metal halide perovskite-based photodetectors (PDs) have attracted great attention because they exhibit extraordinary optoelectronic performances due to advantages such as a low trap-state density and large absorption coefficient. As a buffer layer, G a ₂ O ₃ can block electron hole recombination, passivate an Si surface, reduce trap density, and improve the ability of electron tunneling. Here, we demonstrate a trilayer hybrid structure (S i/G a ₂ O ₃/C H ₃ N H ₃ P b I ₃) composed of an n-type silicon wafer, G a ₂ O ₃ interlayer, and C H ₃ N H ₃ P b I ₃ thin film. The effect of different G a ₂ O ₃ layer thicknesses on the characteristics of a PD was studied, which shows that the responsivity first increases and then decreases with an increase in the G a ₂ O ₃ film thickness; the optimized G a ₂ O ₃ thickness is 300 nm. Additionally, the optimal responsivity, detectivity, and the rise and decay times are 7.2m A W ^-1, 7.448×10¹⁰ Jones, and 39 and 1.7 ms, respectively. This device has a better performance because G a ₂ O ₃ and perovskite have a matched energy level. We believe our work could provide a new way to fabricate high-performance optoelectronic devices.

High-Performance UV-Vis Broad-Spectra Photodetector Based on a β-Ga2O3/Au/MAPbBr3 Sandwich Structure

The UV-vis photodetector (PD), a detector that can simultaneously detect light in the ultraviolet region and the visible region, has a wide range of applications in military and civilian fields. Currently, it is very difficult to obtain good detection performance in the UV region (especially in the solar-blind range) like in the visible region with most UV-vis PDs. This severely affects the practical application of UV-vis broad-spectra PDs. Here, a simple sandwich structure PD (SSPD) composed of β-Ga₂O₃, Au electrodes, and the MAPbBr₃ perovskite is designed and fabricated to simultaneous enhance the detection performance in the UV and visible light regions. The β-Ga₂O₃/Au/MAPbBr₃ SSPD exhibits enhanced optoelectronic performance with high responsivities of 0.47 and 1.43 A W^-1 at 240 and 520 nm under a bias of 6 voltage (V), respectively, which are 8.5 and 23 times than that of the metal-semiconductor-metal (MSM) structure MAPbBr₃ PD at 6 V, respectively. The enhanced performance was attributed to the effective suppression of carrier recombination due to the efficient interface charge separation in the device structure. In addition, the self-powered response characteristic is also realized by forming a type-II heterojunction between β-Ga₂O₃ and MAPbBr₃, which gives the β-Ga₂O₃/Au/MAPbBr₃ SSPD superior single-pixel photo-imaging ability without an external power supply. This work provides a simple and effective method for the preparation of high-performance self-powered imaging PDs in the UV-visible region.

Recent advances in self-powered and flexible UVC photodetectors

Ultraviolet-C (UVC) radiation is employed in various applications, including irreplaceable applications in military and civil fields, such as missile guidance, flame detection, partial discharge detection, disinfection, and wireless communication. Although most modern electronics are based on Si, UVC detection technology remains a unique exception because the short wavelength of UV radiation makes efficient detection with Si difficult. In this review, recent challenges in obtaining ideal UVC photodetectors with various materials and various forms are introduced. An ideal photodetector must satisfy the following requirements: high sensitivity, fast response speed, high on/off photocurrent ratio, good regional selectivity, outstanding reproducibility, and superior thermal and photo stabilities. UVC detection is still in its infancy compared to the detection of UVA as well as other photon spectra, and recent research has focused on different key components, including the configuration, material, and substrate, to acquire battery-free, super-sensitive, ultra-stable, ultra-small, and portable UVC photodetectors. We introduce and discuss the strategies for fabricating self-powered UVC photodetectors on flexible substrates in terms of the structure, material, and direction of incoming radiation. We also explain the physical mechanisms of self-powered devices with various architectures. Finally, we present a brief outlook that discusses the challenges and future strategies for deep-UVC photodetectors.

Earth-abundant and environmentally benign Ni-Zn iron oxide intercalated in a polyaniline based nanohybrid as an ultrafast photodetector

Nickel-zinc iron oxide (NZF) was introduced into a polyaniline (PANI) matrix by an in situ chemical oxidation polymerization approach. The surface composition and chemical states were investigated by X-ray photoelectron spectroscopy (XPS), which revealed an Fe 2p spectrum with the two peak positions of Fe 2p_3/2 and Fe 2p_1/2 at 711.00 and 724.48 eV, respectively. Deconvolution of the Fe 2p_3/2 peak revealed two components with binding energies of 713.98 and 718.16 eV, corresponding to the presence of Fe cations in the octahedral and tetrahedral sites. Additionally, the Rietveld refinement of NZF showed a cubic system with the Fd₃m space group. High-resolution transmission electron microscopy (HRTEM) analysis showed that the NZF material strongly interacts with polyaniline, while the selected area electron diffraction (SAED) pattern perfectly matched with the XRD data. Lognormal distribution was used to determine the particle size, which was found to be in the range of 1-100 nm. A flexible photodetector device utilizing the NZF-PANI nanohybrid was fabricated on an environmentally friendly, biodegradable cellulose paper substrate and the device exhibited excellent performance, i.e., a responsivity of 0.069 A W^-1 and detectivity of 7.258 × 10¹⁰ Jones at a very low voltage of 0.1 V. The non-stretched device showed a responsivity of 24.980 A W^-1 at 5 V, whereas at 2 cm^-1 bending curvature, the device showed a responsivity of 20.175 A W^-1, which was much higher than the responsivity of a commercial photodetector (<0.5 A W^-1).

In Situ Fabrication of PdSe2/GaN Schottky Junction for Polarization-Sensitive Ultraviolet Photodetection with High Dichroic Ratio

Polarization-sensitive ultraviolet (UV) photodetection is of great technological importance for both civilian and military applications. Two-dimensional (2D) group-10 transition-metal dichalcogenides (TMDs), especially palladium diselenide (PdSe₂), are promising candidates for polarized photodetection due to their low-symmetric crystal structure. However, the lack of an efficient heterostructure severely restricts their applications in UV-polarized photodetection. Here, we develop a PdSe₂/GaN Schottky junction by in situ van der Waals growth for highly polarization-sensitive UV photodetection. Owing to the high-quality junction, the device exhibits an appealing UV detection performance in terms of a large responsivity of 249.9 mA/W, a high specific detectivity, and a fast response speed. More importantly, thanks to the puckered structure of the PdSe₂ layer, the device is highly sensitive to polarized UV light with a large dichroic ratio up to 4.5, which is among the highest for 2D TMD material-based UV polarization-sensitive photodetectors. These findings further enable the demonstration of the outstanding polarized UV imaging capability of the Schottky junction, as well as its utility as an optical receiver for secure UV optical communication. Our work offers a strategy to fabricate the PdSe₂-based heterostructure for high-performance polarization-sensitive UV photodetection.

In situ integration of Te/Si 2D/3D heterojunction photodetectors toward UV-vis-IR ultra-broadband photoelectric technologies

Over the past decade, 2D elemental semiconductors have emerged as an ever-increasingly important group in the 2D material family due to their simple crystal structures and compositions, and versatile physical properties. Taking advantage of the relatively small bandgap, outstanding carrier mobility, high air-stability and strong interactions with light, 2D tellurium (Te) has emerged as a compelling candidate for use in ultra-broadband photoelectric technologies. In this study, high-quality centimeter-scale Te nanofilms have been successfully produced by exploiting pulsed-laser deposition (PLD). By performing deposition on pre-patterned SiO₂/Si substrates, a Te/Si 2D/3D heterojunction array is formed in situ. To our delight, taking advantage of the relatively small bandgap of Te, the Te/Si photodetectors demonstrate an ultra-broadband photoresponse from ultraviolet to near-infrared (370.6 nm to 2240 nm), enabling them to serve as important alternatives to conventional 2D materials such as MoS₂. In addition, an outstanding on/off ratio of ∼10⁸ and a fast response rate (a response/recovery time of 3.7 ms/4.4 ms) are achieved, which is associated with the large band offset and strong interfacial built-in electric field that contribute to suppressing the dark current and separating photocarriers. Beyond these, a 35 × 35 matrix array has been successfully constructed, where the devices exhibit comparable properties, with a production yield of 100% for 100 randomly tested devices. The average responsivity, external quantum efficiency and detectivity reach 249 A W^-1, 76 350% and 1.15 × 10¹¹ Jones, respectively, making the Te/Si devices among the best-performing 2D/3D heterojunction photodetectors. On the whole, this study has established that PLD is a promising technique for producing high-quality Te nanofilms with good scalability, and the Te/Si 2D/3D heterojunction provides a promising platform for implementing high-performance ultra-broadband photoelectronic technologies.

Thermally Stable Organic Field-Effect Transistors Based on Asymmetric BTBT Derivatives for High Performance Solar-Blind Photodetectors

High-performance solar-blind photodetectors are widely studied due to their unique significance in military and industrial applications. Yet the rational molecular design for materials to possess strong absorption in solar-blind region is rarely addressed. Here, an organic solar-blind photodetector is reported by designing a novel asymmetric molecule integrated strong solar-blind absorption with high charge transport property. Such alkyl substituted [1]benzothieno[3,2-b][1]-benzothiophene (BTBT) derivatives Cn-BTBTN (n = 6, 8, and 10) can be easily assembled into 2D molecular crystals and perform high mobility up to 3.28 cm² V^-1 s^-1 , which is two orders of magnitude higher than the non-substituted core BTBTN. Cn-BTBTNs also exhibit dramatically higher thermal stability than the symmetric alkyl substituted C8-BTBT. Moreover, C10-BTBTN films with the highest mobility and strongest solar-blind absorption among the Cn-BTBTNs are applied for solar-blind photodetectors, which reveal record-high photosensitivity and detectivity up to 1.60 × 10⁷ and 7.70 × 10¹⁴ Jones. Photodetector arrays and flexible devices are also successfully fabricated. The design strategy can provide guidelines for developing materials featuring high thermal stability and stimulating such materials in solar-blind photodetector application.

High performance polarization-sensitive self-powered imaging photodetectors based on a p-Te/n-MoSe2 van der Waals heterojunction with strong interlayer transition

In-plane anisotropic two-dimensional (2D) materials offer great opportunities for developing novel polarization sensitive photodetectors without being in conjunction with filters and polarizers. However, owing to low linear dichroism ratio and insufficient optical absorption of the few layer 2D materials, the comprehensive performance of the present polarization sensitive photodetectors based on 2D materials is still lower than the practical application requirements. In this work, after systematic investigation of the structural, vibrational, and optical anisotropies of layer-structured Te nanosheets, a novel polarization-sensitive self-powered imaging photodetector with high comprehensive performance based on a p-Te/n-MoSe₂ van der Waals heterojunction (vdWH) with strong interlayer transition is proposed. Owing to the high rectification ratio (10⁴) of the diode, the device shows excellent photovoltaic characteristics. As examples, the photodetectors exhibited an ultrahigh on/off ratio of 10⁵ at a relatively weak light intensity (4.73 mw cm^-2), and the highest responsivity of the device could reach 2106 mA W^-1 without any power supply. In particular, benefitting from the excellent dichroism properties of Te nanosheets synthesized in this work, the anisotropic ratio of the photocurrent (I_max/I_min) could reach as high as 16.39 (405 nm, 24.2 mw cm^-2). This value obtained under zero bias voltage is much greater than that of present 2D material photodetectors even at a bias voltage. In addition, the highest detectivity is 2.91 × 10¹³ Jones at a low bias voltage of -0.08 V. This work provides a novel building block for high resolution polarization-sensitive photodetection of weak signals in complex environments.

Sensing of ultraviolet light: a transition from conventional to self-powered photodetector

Clouds in the sky pass almost 80% of ultraviolet (UV) radiation to the earth's surface, which has a significant impact on humankind. Conventional UV photodetectors (PDs) require an external battery, which not only increases the device size but also has a limited life span and maintenance costs can be prohibitively expensive. An alternative and more technically-sound solution would be the use of self-powered UV PDs that can operate independently, eliminating the need for an external source. Although many exciting studies have been done and state-of-the-art research is underway to successfully fabricate self-powered UV PDs, periodic reviews on this topic are deemed essential so that the technology's readiness can be properly evaluated and critical challenges can be addressed in a timely manner. In this article, the key issues and most exciting developments made in recent years on built-in electric field assisted self-powered UV PDs based on p-n homojunctions, p-n heterojunctions, and Schottky junctions followed by energy harvester integrated UV PDs are extensively reviewed. Finally, a summary and comparison of different types of self-powered UV PDs as well as future challenges that need to be addressed are discussed. This review sets a foundation providing essential insights into the present status of self-powered UV PDs with which researchers can engage and deal with the major challenges.

Boosting the Performance of Self-Powered CsPbCl3-Based UV Photodetectors by a Sequential Vapor-Deposition Strategy and Heterojunction Engineering

All-inorganic CsPbCl₃ perovskite in ultraviolet (UV) detection is drawing increasing interest owing to its UV-matchable optical band gap, ultrahigh UV stability, and superior inherent optoelectronic properties. Almost all of the reported CsPbCl₃ photodetectors employ CsPbCl₃ nano- or microstructures as sensitive components, while CsPbCl₃ polycrystalline film-based self-powered photodetectors are rarely studied on account of the terrible precursor solubility. Herein, a novel sequential vapor-deposition technique is demonstrated to fabricate CsPbCl₃ polycrystalline film for the first time. High-quality CsPbCl₃ films with excellent optical, electronic, and morphological features are obtained. A self-powered photodetector based on the CsPbCl₃ film is constructed without any charge transport layer, showing a high UV detection performance. A thin p-type PbS buffer layer is further introduced to passivate the surface defects of the CsPbCl₃ layer and decrease the interfacial energy barrier by forming a type-II heterojunction, contributing to a faster hole extraction rate and a suppressed dark current level. The best-performing device achieves an ultrafast response time of 1.92 μs, an ultrahigh on/off ratio of 2.22 × 10⁵, and a responsivity of 0.22 A/W upon 375 nm UV illumination at 0 V bias. This comprehensive performance is the best among all of the CsPbCl₃ photodetectors reported to date. The as-prepared photodetectors also present an eminent UV irradiation and long-term durability in ambient air. Furthermore, a large-area and uniform 625-pixel UV image sensor is fabricated and attains a prominent imaging capability. Our work opens a new avenue for the scalable production of CsPbCl₃-based optoelectronics.

Flexible ultraviolet photodetector based on single ZnO microwire/polyaniline heterojunctions

Flexible ultraviolet (UV) photodetectors are considered as potential building blocks for future-oriented photoelectric applications such as flexible optical communication, image sensors, wearable devices and so on. In this work, high-performance UV photodetector was fabricated via a facile combination of single ZnO microwire (MW) and p-type polyaniline. Due to the formation of effective organic/inorganic p-n junction, the as-prepared flexible UV photodetector based on ZnO MW/polyaniline hybrid heterojunction exhibits high performance (responsivity ∼ 60 mA/W and detectivity ∼ 2.0 ×10¹¹ Jones) at the reverse bias of -1 V under the UV illumination. The ZnO MW/polyaniline photodetector displays short response/recovery times (∼ 0.44 s/∼ 0.42 s), which is less than that of most reported UV photodetectors based on ZnO/polymer heterojunction. The fast response speed and recovery speed can be attributed to the high crystallinity of ZnO MW, built-in electric field in space-charge region and the passivation of oxygen traps on the surface. Further, the photodetector using ZnO MW/polyaniline junctions shows excellent flexibility and stability under bent conditions. This work opens a new way to design next-generation high-performance, low-cost and flexible optoelectronic devices for lab-on-a-chip applications.

Solution processed transparent anatase TiO2 nanoparticles/MoO3 nanostructures heterojunction: high performance self-powered UV detector for low-power and low-light applications

Ultraviolet (UV) photodetectors are considered as the major players in energy saving technology of the future. Efforts are needed to further develop such devices, which are capable of operating efficiently at low driving potential as well as with weak illumination. Herein, we report an all-oxide, highly transparent TiO2/MoO3 bilayer film, with nanoparticulate anatase TiO2 as the platform, fabricated by a simple solution based method and demonstrate its use in UV photodetection. Photoconductivity measurement with 352 nm light reveals the self-powered UV detection capability of the device due to the built-in potential at the bilayer interface. The device exhibits a high photoresponsivity (46.05 A W-1), detectivity (2.84 × 1012 Jones) and EQE (16 223%) even with a weak illumination of 76 μW cm-2, at a low bias of only -1 V. The self-powered performance of the bilayer device is comparable to that of commercial Si photodetectors as well as other such UV detectors reported based on metal oxide heterojunctions. The improved and faster photoresponse shown by the device is due to the formation of an effective heterojunction, as evidenced by XPS, electrochemical and I-V studies. It can be further attributed to the better charge transport through the densely aligned nanostructures, reduced recombination and the better mobility of anatase TiO2 nanoparticles. The performance is best-in-class and proves the potential of the transparent heterojunction to be used in highly responsive, self-powered UV detectors for low bias, low light applications.