MOF-Derived In2O3 Microrods for High-Performance Photoelectrochemical Ultraviolet Photodetectors

High-Performance Self-Powered Photoelectrochemical Ultraviolet Photodetectors Based on an In2O3 Nanocube Film

Ultraviolet photodetectors (UV PDs) have attracted significant attention due to their wide range of applications, such as underwater communication, biological analysis, and early fire warning systems. Indium oxide (In2O3) is a candidate for developing high-performance photoelectrochemical (PEC)-type UV PDs owing to its high UV absorption and good stability. However, the self-powered photoresponse of the previously reported In2O3-based PEC UV PDs is unsatisfactory. In this work, high-performance self-powered PEC UV PDs were constructed by using an In2O3 nanocube film (NCF) as a photoanode. In2O3 NCF photoanodes were synthesized on FTO by using hydrothermal methods with a calcining process. The influence of the electrolyte concentration, bias potential, and irradiation light on the photoresponse properties was systematically studied. In2O3 NCF PEC UV PDs exhibit outstanding self-powered photoresponses to 365 nm UV light with a high responsivity of 44.43 mA/W and fast response speed (20/30 ms) under zero bias potential, these results are superior to those of previously reported In2O3-based PEC UV PDs. The improved self-powered photoresponse is attributed to the higher photogenerated carrier separation efficiency and faster charge transport of the in-situ grown In2O3 NCF. In addition, these PDs exhibit excellent multicycle stability, maintaining the photocurrent at 98.69% of the initial value after 700 optical switching cycles. Therefore, our results prove the great promise of In2O3 in self-powered PEC UV PDs.

Self-Assembled BiGaSeAs Composite Superlattice-Structured Nanowire for Broad-Band Photodetection

Photodetectors with a broad-band response range are widely used in many fields and are regarded as pivotal components of the modern miniaturized electronics industry. However, commercial broad-band photodetectors composed of traditional bulk semiconductor materials are still limited by complex preparation techniques, high costs, and a lack of mechanical strength and flexibility, which are difficult to satisfy the increasing demand for flexible and wearable optoelectronics. Therefore, researchers have been devoted to finding new strategies to obtain flexible, stable, and high-performance broad-band photodetectors. In this work, a novel self-assembled BiGaSeAs composite superlattice-structured nanowire was developed with a simple chemical vapor deposition method for easy fabrication. After the device assembling, the photodetector showed outstanding performance in terms of obvious Ion/Ioff (13.9), broad-band photoresponse (365-940 nm), excellent responsivity (1007.67 A/W), high detectivity (9.38 × 109 Jones), and rapid response (21 and 23 ms). The formation of microheterojunctions among various materials inside the nanowires also contributed to their extended broad-spectrum response and outstanding detection ability. These results indicate that the BiGaSeAs nanowires have potential applications in the field of flexible and wearable electronics.

High-Sensitivity Photoelectrochemical Ultraviolet Photodetector with Stable pH-Universal Adaptability Based on Whole Single-Crystal Integrated Self-Supporting 4H-SiC Nanoarrays

Emerging photoelectrochemical (PEC) photodetectors (PDs) have notable advantages over conventional PDs and have attracted extensive attention. However, harsh liquid environments, such as those with high corrosivity and attenuation, substantially restrict their widespread application. Moreover, most PEC PDs are constructed by assembling numerous nanostructures on current collector substrates, which inevitably contain abundant interfaces and defects, thus greatly weakening the properties of PDs. To address these challenges, a high-performance pH-universal PEC ultraviolet (UV) PD based on a whole single-crystal integrated self-supporting 4H-SiC nanopore array photoelectrode is constructed, which is fabricated using a two-step anodic oxidation approach. The PD exhibits excellent photodetection behavior, with high responsivity (218.77 mA W-1 ), detectivity (6.64 × 1013  Jones), external quantum efficiency (72.47%), and rapid rise/decay times (17/48 ms) under 375 nm light illumination with a low intensity of 0.15 mW cm-2 and a bias voltage of 0.6 V, which is fall in the state-of-the-art of the wide-bandgap semiconductor-based PDs reported thus far. Furthermore, the SiC PEC PD exhibits excellent photoresponse and long-term operational stability in pH-universal liquid environments. The improved photodetection performance of the SiC PEC PD is primarily attributed to the synergistic effect of the nanopore array structure, integrated self-supporting configuration, and single-crystal structure of the whole photoelectrode.

Achieving High-Performance Self-Powered Visible-Blind Ultraviolet Photodetection Using Alloy Engineering

The exploration and development of self-powered visible-blind ultraviolet photodetectors (VBUV PDs) with high responsivity and wavelength selectivity have far-reaching significance for versatile applications. Although In2O3 shows potential for UV detection due to good UV absorption and electrical transport properties, the poor wavelength selectivity impedes further application in VBUV PDs. Here, a self-powered photoelectrochemical-type (PEC) VBUV PD is demonstrated by using gallium-indium oxide alloys (Ga-In OAs). The self-powered Ga-In OAs-based PEC VBUV PDs exhibit good VBUV photodetection performance, including a high responsivity of 50.04 mA/W and a high detectivity of 6.03 × 1010 Jones under 254 nm light irradiation, a good wavelength selectivity (UV/visible light rejection ratio of 262.45), and a fast response time (0.45/0.38 s). The good self-powered VBUV detection performance of Ga-In OAs is attributed to the larger band gap and smaller charge-transfer resistance induced by alloy engineering, which not only suppresses the absorption of visible light but also accelerates interfacial charge transfer. Moreover, an underwater optical communication system is demonstrated by using the self-powered Ga-In OAs PEC VBUV PDs. This study demonstrates that alloy engineering is a powerful tool to improve the performance of In2O3-based PEC PDs, and Ga-In OAs have great application potential for underwater optoelectronic devices.

Hydrogen-Terminated Two-Dimensional Germanane/Silicane Alloys as Self-Powered Photodetectors and Sensors

2D monoelemental materials, particularly germanene and silicene (the single layer of germanium and silicon), which are the base materials for modern electronic devices demonstrated tremendous attraction for their 2D layer structure along with the tuneable electronics and optical band gap. The major shortcoming of synthesized thermodynamically very unstable layered germanene and silicene with their inclination toward oxidation was overcome by topochemical deintercalation of a Zintl phase (CaGe₂, CaGe_1.5Si_0.5, and CaGeSi) in a protic environment. The exfoliated Ge-H, Ge_0.75Si_0.25H, and Ge_0.5Si_0.5H were successfully synthesized and employed as the active layer for photoelectrochemical photodetectors, which showed broad response (420-940 nm), unprecedented responsivity, and detectivity on the order of 168 μA W^-1 and 3.45 × 10⁸ cm Hz^1/2 W^-1, respectively. The sensing capability of exfoliated germanane and silicane composites was explored using electrochemical impedance spectroscopy with ultrafast response and recovery time of less than 1 s. These positive findings serve as the application of exfoliated germanene and silicene composites and can pave a new path to practical applications in efficient future devices.

Detach GaN-Based Film to Realize a Monolithic Bifunctional Device for Both Lighting and Detection

Due to the emerging requirements of miniaturization and multifunctionality, monolithic devices with both functions of lighting and detection are essential for next-generation optoelectronic devices. In this work, based on freestanding (In,Ga)N films, we demonstrate a monolithic device with two functions of lighting and self-powered detection successfully. The freestanding (In,Ga)N film is detached from the epitaxial silicon (Si) substrate by a cost-effective and fast method of electrochemical etching. Due to the stress release and the lightening of the quantum-confined Stark effect (QCSE), the wavelength blueshift of electroluminescent (EL) peak is very small (<1 nm) when increasing the injection current, leading to quite stable EL spectra. On the other hand, the proposed monolithic bifunctional device can have a high ultraviolet/visible reject ratio (Q = 821) for self-powered detection, leading to the excellent detection selectivity. The main reason can be attributed to the removal of Si by the lift-off process, which can limit the response to visible light. This work paves an effective way to develop new monolithic multifunctional devices for both detection and display.

2D Few-Layered PdPS: Toward High-Efficient Self-Powered Broadband Photodetector and Sensors

Photodetectors and sensors have a prominent role in our lives and cover a wide range of applications, including intelligent systems and the detection of harmful and toxic elements. Although there have been several studies in this direction, their practical applications have been hindered by slow response and low responsiveness. To overcome these problems, we have presented here a self-powered (photoelectrochemical, PEC), ultrasensitive, and ultrafast photodetector platform. For this purpose, a novel few-layered palladium-phosphorus-sulfur (PdPS) was fabricated by shear exfoliation for effective photodetection as a practical assessment. The characterization of this self-powered broadband photodetector demonstrated superior responsivity and specific detectivity in the order of 33 mA W^-1 and 9.87 × 10¹⁰ cm Hz^1/2 W^-1, respectively. The PEC photodetector also exhibits a broadband photodetection capability ranging from UV to IR spectrum, with the ultrafast response (∼40 ms) and recovery time (∼50 ms). In addition, the novel few-layered PdPS showed superior sensing ability to organic vapors with ultrafast response and a recovery time of less than 1 s. Finally, the photocatalytic activity in the form of hydrogen evolution reaction was explored due to the suitable band alignment and pronounced light absorption capability. The self-powered sensing platforms and superior catalytic activity will pave the way for practical applications in efficient future devices.

Ultrathin In2 O3 Nanosheets toward High Responsivity and Rejection Ratio Visible-Blind UV Photodetection

Photoelectrochemical-type visible-blind ultraviolet photodetectors (PEC VBUV PDs) have gained ever-growing attention due to their simple fabrication processes, uncomplicated packaging technology, and high sensitivity. However, it is still challenging to achieve high-performance PEC VBUV PDs based on a single material with good spectral selectivity. Here, it is demonstrated that individual ultrathin indium oxide (In₂ O₃ ) nanosheets (NSs) are suitable for designing high-performance PEC VBUV PDs with high responsivity and UV/visible rejection ratio for the first time. In₂ O₃ NSs PEC PDs show excellent UV photodetection capability with an ultrahigh photoresponsivity of 172.36 mA W^-1 and a high specific detectivity of 4.43 × 10¹¹ Jones under 254 nm irradiation, which originates from the smaller charge transfer resistance (R_ct ) at the In₂ O₃ NSs/electrolyte interface. The light absorption of In₂ O₃ NSs takes a blueshift due to the quantum confinement effect, granting good spectral selectivity for visible-blind detection. The UV/visible rejection ratio of In₂ O₃ NSs PEC PDs is 1567, which is 30 times higher than that of In₂ O₃ nanoparticles (NPs) and exceeds all recently reported PEC VBUV PDs. Moreover, In₂ O₃ NSs PEC PDs show good stability and good underwater imaging capability. The results verify that ultrathin In₂ O₃ NSs have potential in underwater optoelectronic devices.