Nanocrystalline ZnFe₂O₄ (ZFO) particles were synthesized using a microwave-assisted solid-state reaction (MW–SSR), and their phase formation kinetics were systematically investigated. Differential scanning calorimetry revealed an exceptionally low activation energy for crystallization ( 5.1 kJ·mol⁻1), several times lower than values reported for conventional solid-state reaction method. This reduction highlights the strong influence of microwave irradiation in accelerating spinel phase formation. In contrast, the activation energy for grain growth ( 38 kJ·mol⁻1) was found to be higher than in conventional methods, suggesting that microwave processing promotes rapid nucleation while suppressing coarsening, thereby stabilizing nanoscale crystallites ( 35 nm). Structural and optical analyses confirmed phase-pure ZFO with a bandgap of 1.9 eV, while morphological studies showed uniform particle distribution. Photocatalytic tests on methylene blue degradation demonstrated visible-light activity comparable to solid-state synthesized ZFO. These findings extend new kinetic insights into microwave-driven crystallization and growth to the past studies. The results establish MW–SSR method as a rapid, energy-efficient, and scalable approach for fabricating functional ferrites with potential applications in photocatalysis and related areas.

Solution-processed photodetectors have attracted significant research interest due to their multimodal functionalities, ease of fabrication, and compatibility with various substrates. However, these devices often face challenges such as limited performance and slow response times. This study reports the development of a zero-bias photodetector employing a p-n junction heterostructure that combines environmentally benign copper tin sulfide (Cu2SnS3, CTS) with low-temperature-processed TiO2 nanorods. CTS, a nontoxic and earth-abundant chalcogenide, was deposited onto hydrothermally synthesized TiO2 nanorods via chemical bath deposition, resulting in a robust and efficient CTS/TiO2 heterostructure. XRD analysis revealed the rutile phase of TiO2 and the mixed tetragonal-wurtzite phases of Cu2SnS3. The heterojunction demonstrated broad spectral absorption across the UV-visible range, with TiO2 (3.1 eV) absorbing primarily UV light and Cu2SnS3 (1.75 eV) effectively covering the visible spectrum. I-V characteristics depicted a nonlinear relationship, indicating the presence of a built-in potential at the p-n junction, which enhances photocurrent generation under illumination. Notably, the detector operates efficiently at 0 V, highlighting its self-powered capability. Temporal response analysis revealed rapid rise and fall times (similar to 40 ms), emphasizing the potential of this solution-processed heterostructure for fast and reliable photodetection. The detector exhibited excellent performance metrics, including a low dark current (477 nA), high photocurrent (15.7 mu A), high ON/OFF ratio (33), and high responsivity (50 mA/W). The nanorod heterostructure architecture offers conformable junction between Cu2SnS3 and TiO2 and thereby offers an efficient pathway for photocarrier collection. The demonstrated CTS-TiO2 nanorod detector is promising for the development of sustainable photodetectors for various potential applications, viz., environmental monitoring, medical diagnostics, and portable electronics.

Multispectral photodetectors are essential for diverse applications such as machine vision, quantum computing, and wafer inspection. Conventional detectors often rely on epitaxially grown materials such as Si and InGaAs, which involve complex fabrication processes. In this study, we present a self-powered Vis-NIR photodetector based on a hybrid bulk heterostructure of SnS-Bi2Te3-PEDOT:PSS, fabricated entirely through solution-based techniques. A spray-pyrolyzed SnS film serves as the photoactive layer onto which exfoliated Bi2Te3 integrated with PEDOT:PSS is deposited, forming a vertical heterojunction. Structural analysis via X-ray diffraction and Raman techniques confirms the successful formation of SnS and Exfoliated Bismuth Telluride. Optical studies reveal enhanced absorption in the near-infrared (NIR) region. Bi2Te3, an ultranarrow bandgap semiconductor (E-g similar to 0.15 eV), and SnS, a narrow bandgap (E-g similar to 1.0 eV) layered semiconductor, offer strong light absorption in the visible and NIR ranges. The device demonstrates a spectral response from Visible to NIR, with a peak responsivity of 3.78 mA/W and a fast response time of 86 ms at zero bias. Mechanistic studies indicate that the photothermoelectric effect from Bi2Te3 and PEDOT:PSS enhances the NIR response, while SnS contributes predominantly through photovoltaic effect in the visible range, aided by efficient hole transport from PEDOT:PSS. The detector maintains high stability over >500 photocycles and offers a facile route to scalable, low-cost multispectral photodetection. This work provides critical insight into the interplay between photovoltaic and photothermoelectric effects in hybrid heterostructures and highlights the potential of Bi2Te3-based detectors for ambient light sensing and photonic applications.

Hybrid heterojunction between organic PEDOT:PSS and inorganic Silicon (Si) nanostructures is promising for high-performance self-powered photodetectors due to their favourable band energetics and ease of processing. Traditionally, Si nanostructures require additional passivation layers to reduce surface defect states, which adds complexity and involves the use of harmful organic solvents. Here in, we demonstrate a simple chemical polishing process to reduce defects and fabricate a conformable heterojunction between Si nanostructures and PEDOT:PSS. Si nanostructures fabricated by metal-assisted chemical etching (MACE) technique and subsequently treated by the chemical polishing process are spin-coated with PEDOT:PSS to form heterojunction and employed as self-powered broadband photodetector. The optimized device shows superior performance, such as high responsivity of 555.34 mA/W, quick rise/fall times of 79 ms/81 ms, high External Quantum Efficiency (EQE) of 0.8 at zero bias (0 V) and high photostability up to 500 illumination cycles. Dark I-V characteristics and carrier lifetime measurements reveal that the enhanced performance of chemically polished devices is attributed to the formation of a conformable heterojunction and reduction in defects in the Si nanostructures. Given the scalability and simplicity of the demonstrated passivation-free approach, this work may aid the fabrication of high-performance hybrid Si nanostructured photodetectors.

Silicon (Si) photodetectors do not efficiently capture photons in the UV region: this has been a major impediment to their application in several areas. However, quantum dots (QDs), which convert higher-energy photons into lower-energy photons via spectral downshifting, have emerged as promising candidates for enhancing the UV response of silicon photodetectors. In this study, we investigate the performance of Si photodetectors in the form of sensitized perovskite (CsPbBr3) quantum dots and compare them with core-shell (CdZnS/ZnS) quantum dots for spectral downshifting applications. Using monolithic integration of quantum dots over the silicon photodetector surface, we systematically analyze their electrical and optical characteristics to elucidate the impact of quantum dot structures on device performance. Spectral responsivity measurements reveal a significant enhancement in detector performance over a broad spectral range (300nm - 1100nm) after sensitization with quantum dots. Reflectance studies suggest that apart from spectral downshifting, the quantum dot layers act as anti-reflection coatings, contributing to overall performance enhancement. Additionally, current-voltage characteristics indicate the formation of a space charge region at the Si-quantum dot interface, further enhancing device performance. Further opto-electronic testing demonstrates the superior performance and stability of CdZnS/ZnS core-shell QD-sensitized devices compared to perovskite CsPbBr3 QD-devices. Our study provides valuable insights into the design and optimization of Si photodetectors with improved sensitivity and extended spectral response.

Despite their ubiquity, Silicon (Si)-based photodetectors face intrinsic limitations that inhibit their performance, especially in the critical ultraviolet (UV) range. Downshifting of high energy photons by employing luminescent quantum dots (QDs) has up to now been the commonest photon harvesting technique in Si photodetectors. This research article describes the monolithic integration of CdZnS/ZnS core-shell QDs with Si photodetectors to make use of the spectral downshifting effect. Silicon detectors sensitised with these QDs have shown remarkably enhanced responsivity and external quantum efficiency over a broad spectral range of 300 - 1100 nm. Apart from the spectral down-shifting process, the anti-reflection effect of the QD film and the formation of a space charge region at the Si-CdZnS/ZnS interface have also contributed to enhanced device performance. The additive effect of spectral downshifting, anti-reflection effects and heterojunction formation has given these QD-sensitized devices enhanced responsivity and EQE values of 345 mA/W and 0.5, markedly higher than the values of 110 mA/W and 0.15 seen in pristine devices. Given the notable enhancement demonstrated without the need for the application of epitaxial techniques, this study may assist in mitigating the inherent limitations of Si photodetectors.

Conventional Lead-based hybrid perovskite photodetectors face significant challenges due to toxicity and poor ambient stability. This study contributes to the development of sustainable and efficient photodetectors by leveraging the exceptional properties of Lead-free Cs2AgBiBr6 double perovskite. A key feature of this work is the use of Cs2AgBiBr6 in a hole transport material (HTM)-free architecture with carbon electrodes, simplifying fabrication and enhancing device stability. The Cs2AgBiBr6 films are fabricated using a one-step spin-coating method under ambient conditions. Structural and optical analysis confirms the formation of a cubic perovskite phase with a 2.02 eV bandgap. The photodetector operates in a self-powered mode, detecting a broad spectral range from 350 to 600 nm, with impressive responsivity (50 mA/W), detectivity (5.1 x 10(11) Jones), and a fast rise time (160 ms). The Type-II band alignment at the Cs2AgBiBr6-TiO2 interface enables the self-powered operation. The inherent structural stability of Cs2AgBiBr6 results in excellent durability, maintaining performance over multiple photocycles (>500), prolonged exposure to simulated sunlight (>1 h), high humidity (RH similar to 90 % for 4 h), and elevated temperatures (80 degrees C for 4 h). Moreover, the device retained its responsivity for more than 60 days when stored under ambient conditions without encapsulation. With its simplified HTM-free architecture and Carbon electrode, the detector exhibits excellent photoresponse and resilience under harsh conditions, demonstrating the potential of Cs2AgBiBr6 in addressing the lead toxicity and stability issues in photodetectors.

Developing highly active, stable, and economic electrocatalysts for sustainable hydrogen (H-2) production is crucial for efficient water electrolysis. In this study, a highly effective and affordable electrocatalyst for hydrogen evolution was developed using an easy and straightforward one-step hydrothermal method for in situ doping of Pd into the lattice of MoS2. The physico-chemical and electrochemical properties of the as-prepared Pd-doped MoS2 systems were thoroughly studied. After Pd was doped into the MoS2 lattice, sulfur vacancies were induced, which led to a phase change from the semiconducting (2H) to the metallic (1T) phase of MoS2. These changes altered the material's morphology and optimized its electronic structure, making it a superior electrocatalyst for water splitting. The electrocatalytic activity of a cathode prepared via drop-casting using Pd-MoS2 nanostructured powder for HER applications was studied in acidic water, alkaline water, and simulated sea water. In order to attain a current density of 10 mA cm(-2) during HER application, nanostructured Pd-MoS2 exhibited greater electrocatalytic activity in acidic conditions with an overpotential of only 89 mV vs. RHE (acidic) compared to 149 mV vs. RHE (alkaline) and 165 mV vs. RHE (simulated sea water). Moreover, in acidic, alkaline, and simulated sea water, Pd-MoS2 demonstrated superior activity during electrocatalytic water splitting and low cell potentials of +1.98, +2.03, and +2.18 V, respectively. This study demonstrates that Pd doping makes MoS2 a promising candidate for the HER and electrocatalytic water splitting compared to expensive metals.

(100) layered Aurivillius-phase perovskite single-phase PbBi2Nb2O9 (PBNO) photocatalyst was reported to be an efficient photocatalyst as compared to the conventionally known visible light photocatalyst of N doped TiO2 (NTO). We report here the specific photoluminescence studies of PBNO to understand its improved photocatalytic property. We have synthesized PBNO and NTO photocatalyst films. Further, their structural, optical and photocatalytic degradation properties have been studied. PBNO demonstrated superior methylene blue degradation as compared to NTO, under visible light photons. The steady-state and time-resolved photoluminescence (PL) studies were specially utilized at characterization tool to understand reason of the high photocatalytic activity of PBNO. We analyzed how high crystallinity of PBNO, and the longer recombination lifetime due to charge separation during photocatalytic reaction yields improved activity in PBNO as compared to NTO. Accordingly, mechanistic scheme for methylene blue photodegradation under solar light photons has been proposed. This study also indicates importance of photoluminescence study for photocatalysts.

Solution processed photodetectors have garnered great attention in applications such as, machine vision perception, neuromorphic computing and opto-electronic memory storage. Though, such photodetectors offer several advantages such as ease of fabrication, high scalability, low thermal budget and low-cost processing, multi-modal functionality etc. however, they suffer from the major drawback of inferior device performance -as low responsivity and slow rise time, particularly due to the intrinsic poor crystallinity of the photoactive material. In this work, we demonstrate a solution processed photodetector with impressive performance at comparatively low processing temperatures (<150 degrees C) based on the mixed dimensional heterostructure configuration of 1D TiO2 nanorods and 3D CdS nanoflowers. TiO2 nanorods have been synthesized by hydrothermal technique, whereas their CdS sensitization is done by chemical bath deposition. Low cost carbon paste is used as electrode instead of conventional non-economic noble metal electrodes. X-ray diffraction studies validated excellent crystallinity of the photoactive material even under low temperature processing condition. The type-II Heterojunction (TiO2 and CdS) configuration photodetector shows efficient response at zero bias, thus yielding a self-powered device. The detector shows response in UV and visible region, with excellent responsivity of 110 mA/W (5 V), 563 A/W (0 V) and a quicker rise time of 81 ms. Albeit the simple fabrication scheme and low processing temperatures, the detector exhibited promising figures-of-merit, which aids in fabrication of novel solution processed photodetectors.

Methylammonium lead Iodide (MAPbI3) is emerging as the frontrunner for high-performance photo-detection due to its superior optoelectronic characteristics and ease of processing. Titanium dioxide (TiO2) is the commonly employed electron transport layer in conventional perovskite-based photodetectors. However, the fundamental understanding of the role of TiO2 morphology and its thickness on the photodetector performance is yet to be explored explicitly. This work systematically investigates the impact of morphology (mesoporous versus compact TiO2 layer) and thickness of the TiO2 layer (50 nm - 3000 nm) on the MAPbI3 photodetector performance. The devices have been fabricated in a hole transport material (HTM)-free architecture with carbon as the top contact. The heterojunction between MAPbI3 and TiO2 renders the device with self-powered capability. The influence of the perovskite sensitisation in the TiO2 electrodes, carrier recombination characteristics and charge-carrier transfer resistances have been studied using photoluminescence and impedance spectroscopy. The TiO2 layer morphology and thickness affected the MAPbI3 infiltration and film formation kinetics. Impedance and photo-luminescence spectroscopies reveal that TiO2 layers, with thickness above 460 nm, negatively affected the device performance. An optimum thickness of 460 nm-mesoporous TiO2 layer exhibited a superior responsivity and rise time of 2.9 A/W and 21 ms, respectively. The poor performance at higher thicknesses is due to the increased interfacial charge transfer resistance and charge carrier recombination. This work is the first report of extensive optimisation and study on the impact of TiO2 film morphology and thickness on the MAPbI3 photodetectors. The present work will be a key for modelling and designing high-performance perovskite photodetectors.

Methyl ammonium lead halide (MAPbX 3 ) suffers from high toxicity of the Pb 2+ cation leading to a major roadblock to its end-application. Replacement of Pb 2+ MAPbX 3 with Mg 2+ would lower its toxicity.

Hybrid organic-inorganic composites offer solution processability and ease to construct opto-electronic devices with diverse functionalities, which are desirable for applications like flexible and printed electronics. Trigonal Selenium (t-Se) has been recently investigated for photodetector application, owing to its inherent superior optical properties such as high absorption coefficient and photoconductivity. However, most of the reported Selenium photodetectors use vapor transport based device fabrication techniques which require controlled en-vironments and face scalability issues. In this work, high-performance photodetector based on Selenium-PEDOT: PSS hybrid junction is demonstrated using a facile sonication assisted mechanical mixing and drop-casting technique. XRD and Raman analysis reveals the existence of Selenium in trigonal crystal structure and FE-SEM images show clustered nanoparticles. Selenium is mixed with PEDOT:PSS to form bulk heterojunction, which enhances the electron-hole pair separation efficiency and results in improved device responsivity. Also, due to the favorable band offset between Selenium and PEDOT:PSS which results in built-in field, the photo-detector operates in self-biased mode. The device exhibits broad spectral response in UV-Vis-NIR range with responsivities of 0.56 A/W, 66 mA/W and 1.363 A/W at 315 nm, 620 nm and 820 nm, respectively. Response times of 7.7 s, 9.4 s and 6.4 s and external quantum efficiencies (EQE) of 192.58%, 13.25% and 206.55% are obtained for UV, Vis and NIR spectra respectively. Further to validate the robustness, the device is subjected to multiple bending cycles (~2500) and minimal degradation in performance is observed. Given the simple device architecture and facile device fabrication scheme, this work would enable promising approach for high perfor-mance flexible photodetectors.

Solution processed photodetectors with high responsivities and simple fabrication schemes are high on demand for variety of emerging opto-electronic applications. However, these devices suffer from sluggish response and recovery times. In this work, we demonstrate the simultaneous enhancement of the responsivity, response time and spectral range of detection in a solution-processed device based on organic/ inorganic hybrid junction. A solution-processed flexible CdS photodetector is fabricated using a facile and economical chemical bath deposition technique. The fabricated pristine-CdS device exhibits responsivity and response time of 50 mA/W and 5.4 s. The resultant device exhibits enhanced responsivity and response time of around 740 mA/W and 0.6 s, respectively, upon modification with the PEDOT:PSS conducting polymer. These values of PEDOT-modified device are one order larger than pristine-CdS detector. Further, PEDOT:PSS modification also extends the responsivity of the device from UV-Vis to NIR spectra. NIR responsivity in the hybrid device, is imputed to the photothermal property of the PEDOT:PSS layer. Thus, the overall device spectral response is accredited to the simultaneous existence of photoelectric and photo thermal phenomena. The observed responsivity and faster response time is ascribed primarily to the builtin potential at interface of CdS-PEDOT:PSS, which not only facilitates efficient separation of photo carriers but also leads to a reduction in the recombination of excitons. Given the simple approach and excellent enhancement in the device performance, the idea demonstrated here could be useful to design high performance opto-electronic device based on solution-processed techniques.(c) 2022 Elsevier B.V. All rights reserved.

Conventional heterojunction photodetectors rely on planar junction architecture which suffer from low interfacial contact area, inferior light absorption characteristics and complex fabrication schemes. Heterojunctions based on mixed dimensional nanostructures such as 0D-1D, 1D-2D, 1D-3D etc have recently garnered exceptional research interest owing to their atomically sharp interfaces, tunable junction properties such as enhanced light absorption cross-section. In this work, a flexible broadband UV-vis photodetector employing mixed dimensional heterostructure of 1D NiO nanofibers and 3D Fe2O3nanoparticles is fabricated. NiO nanofibers were synthesized via economical and scalable electro-spinning technique and made composite with Fe2O3nanoclusters for hetero-structure fabrication. The optical absorption spectra of NiO nanofibers and Fe2O3nanoparticles exhibit peak absorption in UV and visible spectra, respectively. The as-fabricated photodetector displays quick response times of 0.09 s and 0.18 s and responsivities of 5.7 mA W-1(0.03 mW cm-2) and 5.2 mA W-1(0.01 mW cm-2) for UV and visible spectra, respectively. The fabricated NiO-Fe2O3device also exhibits excellent detectivity in the order of 1012jones. The superior performance of the device is ascribed to the type-II heterojunction between NiO-Fe2O3nanostructures, which results in the localized built-in potential at their interface, that aids in the effective carrier separation and transportation. Further, the flexible photodetector displays excellent robustness when bent over ∼1000 cycles thereby proving its potential towards developing reliable, diverse functional opto-electronic devices.

A hybrid organic–inorganic bulk heterojunction for broadband photodetection.

There are tremendous efforts to realize the idea of employing photoelectrochemical (PEC) technology for generating chemical energy from solar energy. The most important feature of this technology is to coordinate the energetics of an electrochemical reaction with the solar spectrum. So, the photoelectrochemistry of a semiconducting material plays a vital role in this arena. Exploring an efficient and stable semiconductor material for such purpose is an essential prospect. There are several sulfide selenide-based semiconductors viz. II-VI (Zn/Cd = S/Se) semiconductors those exhibit high potential in PEC application. Nonetheless, they suffer by certain corrosion issues, which are important to be reviewed and are discussed here. This review highlights the significant role of cadmium chalcogenides among various materials explored in this technology. CdS is the most studied system among all those with perfect band gap and band-edge position exhibiting material, desired for photoanode in PEC cell. Next, recent progresses achieving enhancement in the performance of CdS photoanodes by doping, modifying the surface, morphology reconstruction, and engraving heterostructure is discussed in detail. The role of the nanostructured techniques, improved photo electrochemistry with redox couples, and advanced interfacial and band gap engineering is explored to overcome the lack of chemical stability of CdS. The review concludes with the bright scope of CdS as an efficient PEC material in the form of combined semiconductor systems with an optimum band gap, bandedge, and their complimentary properties rather than a single component material.

Hydrothermally synthesized nanostructured MoS 2 was immobilized over large area graphite paper (5 × 5 mm 2 ) to fabricate electrode for hydrogen evolution application. The chemical optimization via. variation in hydroxylamine hydrochloride(HAH) concentration, led to nanosheets containing surface over the micro-balls, with a 1T and 2H phase of MoS 2 . A physicochemical and electrochemical characterization yielded a lowest Tafel slope of ∼67 mV dec −1 , a lowest over potential of 0.19 V with a significant electrocatalytic stability in acidic. An electrocatalytic hydrogen evolution over optimized MoS 2 evolved 2 times (∼46 μ mol h −1 ) of hydrogen gas as compared to that from MoS 2 synthesized without HAH. The improved performance of electrocatalyst can be attributed to the combination of phase, and electrochemical properties 2D structure of MoS 2 .

Deposition of nickel phosphide film is crucial in electronic fabrication industries as well as a hydrogen generating energy material. Accordingly, the film adhesion on various substrates like insulators (Al2O3, SiO2, etc.) or conductors (glassy carbon, graphite, transparent conductors-FTO etc.) is highly important, specially for printed circuit boards. It has technologically important properties wrt. high temperature thermally stablity, anti-corrosion, large wear resistance, and competitive over-potential wrt Pt metal (for fuel cell). We tackeled the challenge of depositing an adherent nickel phosphide (Ni-P) film on the graphite (GR) substrate by using economic electroless (EL) technique. Firstly, the GR surface was activated by thermal treatment of GR under O-2 atmospheres, and obtained activated GR. Secondly, the EL precursor concentration was varied in the range of 0.1-0.2 M, to study its effect on Ni:P stoichiometry, structural phase and film thickness of Ni-P film on activated GR. Unlike on as recieved GR, activated GR showed film deposition due to the possible diffusion of O-2 over the top layers of GR surface, during activation process. Such O-2 diffusion led to an increased inter-planar distance & thus rendered favourable catalytic sites for Ni & P ions during EL deposition. This yeilds an adherent film of Ni3P phase after thermal treament, which is known to be themally stable beyond 1000 degrees C. Ni-P/GR film shows high potential application in (i) HER (hydrogen evolution reaction) for electro catalytic energy generation, and in (ii) graphite boat usable under elevated temperatures.