The improved photoresponse properties of self-powered NiO/ZnO heterojunction arrays UV photodetectors with designed tunable Fermi level of ZnO

Self-powered photodetectors: a device engineering perspective

Nanoscale self-powered photodetectors that can work without any external source of energy are required for future applications. There is potential demand for these devices in areas like wireless surveillance, weather forecasting, remote monitoring, and places where the availability of power is scarce. This study provides an overview of state of the art research trends and improvements in self-powered photodetectors. A device engineering perspective for improvement in the figures of merit has been presented along with a description of additional effects like pyro-phototronic, piezo-phototronic, and surface plasmonics.

Air-stable self-powered photodetector based on TaSe2/WS2/TaSe2 asymmetric heterojunction with surface self-passivation

Two-dimensional (2D) transition metal dichalcogenides are highly suitable for constructing junction photodetectors because of their suspended bond-free surface and adjustable bandgap. Additional stable layers are often used to ensure the stability of photodetectors. Unfortunately, they often increase the complexity of preparation and cause performance degradation of devices. Considering the self-passivation behavior of TaSe2, we designed and fabricated a novel self-powered TaSe2/WS2/TaSe2 asymmetric heterojunction photodetector. The heterojunction photodetector shows excellent photoelectric performance and photovoltaic characteristics, achieving a high responsivity of 292 mA/W, an excellent specific detectivity of 2.43 × 1011 Jones, a considerable external quantum efficiency of 57 %, a large optical switching ratio of 2.6 × 105, a fast rise/decay time of 43/54 μs, a high open-circuit voltage of 0.23 V, and a short-circuit current of 2.28 nA under 633 nm laser irradiation at zero bias. Moreover, the device also shows a favorable optical response to 488 and 532 nm lasers. Notably, it exhibits excellent environmental long-term stability with the performance only decreasing ∼ 5.6 % after exposed to air for 3 months. This study provides a strategy for the development of air-stable self-powered photodetectors based on 2D materials.

Boosting Charge Utilization in Self-Powered Photodetector for Real-Time High-Throughput Ultraviolet Communication

Ultraviolet (UV) communication is a cutting-edge technology in communication battlefields, and self-powered photodetectors as their optical receivers hold great potential. However, suboptimal charge utilization has largely limited the further performance enhancement of self-powered photodetectors for high-throughput communication application. Herein, a self-powered Ti3 C2 Tx -hybrid poly(3,4 ethylenedioxythiophene):poly-styrene sulfonate (PEDOT:PSS)/ZnO (TPZ) photodetector is designed, which aims to boost charge utilization for desirable applications. The device takes advantage of photothermal effect to intensify pyro-photoelectric effect as well as the increased conductivity of the PEDOT:PSS, which significantly facilitated charge separation, accelerated charge transport, and suppressed interface charge recombination. Consequently, the self-powered TPZ photodetector exhibits superior comprehensive performance with high responsivity of 12.3 mA W-1 and fast response time of 62.2 µs, together with outstanding reversible and stable cyclic operation. Furthermore, the TPZ photodetector has been successfully applied in an integrated UV communication system as the self-powered optical receiver capable of real-time high-throughput information transmission with ASCII code under 9600 baud rate. This work provides the design insight of highly performing self-powered photodetectors to achieve high-efficiency optical communication in the future.

Research advances in ZnO nanomaterials-based UV photode tectors: a review

Ultraviolet photodetectors (UV PDs) have always been the research focus of semiconductor optoelectronic devices due to their wide application fields and diverse compositions. As one of the best-known n-type metal oxides in third-generation semiconductor electronic devices, ZnO nanostructures and their assembly with other materials have received extensive research. In this paper, the research progress of different types of ZnO UV PDs is reviewed, and the effects of different nanostructures on ZnO UV PDs are summarized in detail. In addition, physical effects such as piezoelectric photoelectric effect, pyroelectric effect, and three ways of heterojunction, noble metal local surface plasmon resonance enhancement and formation of ternary metal oxides on the performance of ZnO UV PDs were also investigated. The applications of these PDs in UV sensing, wearable devices, and optical communication are displayed. Finally, the possible opportunities and challenges for the future development of ZnO UV PDs are prospected.

High-Performance NiO/TiO2/ZnO Photovoltaic UV Detector

The ultraviolet (UV) photodetector has found many applications, ranging from optical communication to environmental monitoring. There has been much research interest in the development of metal oxide-based UV photodetectors. In this work, a nano-interlayer was introduced in a metal oxide-based heterojunction UV photodetector to enhance the rectification characteristics and therefore the device performance. The device, which consists of nickel oxide (NiO) and zinc oxide (ZnO) sandwiching an ultrathin dielectric layer of titanium dioxide (TiO₂), was prepared by radio frequency magnetron sputtering (RFMS). After annealing, the NiO/TiO₂/ZnO UV photodetector exhibited a rectification ratio of 10⁴ under UV irradiation of 365 nm at zero bias. The device also demonstrated a high responsivity of 291 A/W and a detectivity of 6.9 × 10¹¹ Jones at +2 V bias. Such a device structure provides a promising future for metal oxide-based heterojunction UV photodetectors in a wide range of applications.

Self-powered p-CuI/n-GaN heterojunction UV photodetector based on thermal evaporated high quality CuI thin film

With vacuum thermal evaporation, the CuI film was deposited on quartz and n-GaN substrates, and the morphology, crystalline structure and optical properties of the CuI films were investigated. According to the XRD results, the CuI film preferentially grew along [111] crystal orientation on the GaN epilayer. With Au and Ni/Au ohmic contact electrodes fabricated on CuI and n-GaN, a prototype p-CuI/n-GaN heterojunction UV photodetector strong UV spectral selectivity was created. At 0 V and 360 nm front illumination (0.32 mW/cm²), the heterojunction photodetector displayed outstanding self-powered detection performance with the responsivity (R), specific detectivity (D*), and on/off ratio up to 75.5 mA/W, 1.27×10¹² Jones, and ∼2320, respectively. Meanwhile, the p-CuI/n-GaN heterojunction photodetector had excellent atmosphere stability.

Self-powered UV photodetectors and imaging arrays based on NiO/IGZO heterojunctions fabricated at room temperature

Self-powered UV photodetectors and imaging arrays based on p-type NiO/n-type InGaZnO (IGZO) heterojunctions are fabricated at room temperature by using ratio-frequency magnetron sputtering. The p-n heterojunction exhibits typical rectifying characteristics with a rectification ratio of 7.4×10⁴ at a ±4 V applied bias. A high photo-responsivity of 28.8 mA/W is observed under zero bias at a wavelength of 365 nm. The photodetector possesses a fast response time of 15 ms which is among the best in reported oxide-based p-n junction-based UV photodetectors. Finally, recognition of an "H" pattern is demonstrated by a 10×10 photodetector array at zero bias. The results indicate that the NiO/IGZO based photodetectors may have a great potential in constructing large-scale self-powered UV imaging systems.

Laser ablation fabrication of ap-NiO/n-Si heterojunction for broadband and self-powered UV-Visible-NIR photodetection

We report on the optoelectronic characteristics ofp-NiO/n-Si heterojunction photodiode for broadband photodetection, fabricated by depositing ap-type NiO thin film onto a commercialn-type silicon substrate using pulsed laser deposition (PLD) technique. The structural properties of the PLD-grownp-NiO material were analysed by means of x-ray diffraction and x-ray photoelectron spectroscopy, confirming its crystalline nature and revealing the presence of Ni vacancies, respectively. Hall measurements confirmed thep-type semiconducting nature of the NiO thin film having a carrier concentration of 8.4 × 10¹⁶cm^-3. The current-voltage (I-V) characteristics of thep-NiO/n-Si heterojunction photodevice were investigated under different wavelengths ranging from UV to NIR. The self-bias properties under different illuminations of light were also explored systematically. Under self-bias condition, the photodiode exhibits excellent responsivities of 12.5 mA W^-1, 24.6 mA W^-1and 30.8 mA W^-1with illumination under 365 nm, 485 nm, and 850 nm light, respectively. In addition, the time dependency of the photoresponse of the fabricated photodevice has also been investigated and discussed thoroughly.

Self-powered broadband photodetector based on a solution-processed p-NiO/n-CdS:Al heterojunction

Solution-processed photodetectors have emerged as the next generation of sensing technology owing to their ease of integration with electron devices and of tuning photodetector performance. Currently, novel self-powered photodetectors without an external power source, for use in sensing, imaging and communication, are in high demand. Herein, we successfully developed a self-powered photodetector based on a novel solution-processed p-NiO/n-CdS:Al heterojunction, which shows an excellent current rectification characteristic ratio of up to three orders in the dark and distinctive photovoltaic behavior under light illumination. The complete solution synthesis route followed the development of CdS:Al thin films on ITO substrates by chemical bath deposition and NiO thin films by the sol-gel route. Optical absorption data revealed that NiO is more active in the UV region and CdS:Al has a majority of absorption in the visible region; so, upon light illumination, the effective separation of photogenerated carriers produces fast photodetection in the UV-visible region. The photoresponsivity values of the fabricated device were calculated to be 55 mA W^-1 and 30 mA W^-1 for UV and visible illumination, respectively. Also, the device has a fast rise and decay photoresponse speed at zero bias voltage, due to the self-driven photovoltaic effect which makes this heterojunction a self-powered device. This complete solution and new method of fabrication make it possible to combine different materials and flexible substrates, enhancing its potential applications in photodetectors, optoelectronic devices and sensors.