High Photocurrent Research Articles

Enhanced Photo-Electrochemical Responses through Photo-Responsive Ruthenium Complexes on ITO Nanoparticle Surface

The mononuclear ruthenium 1-Cl and dinuclear ruthenium 2-Cl complexes undergo a photo-induced ligand exchange in water, affording the corresponding 1-H2O and 2-H2O complexes. The use of indium tin oxide nanoparticles (nanoITOs) to explore the photo-electrochemistry of the in situ-generated 1-H2O and 2-H2O in solution revealed greater photocurrents produced by these two complexes when compared with an experiment using a buffer only. Interestingly, the high photocurrent shown by the dinuclear complex 2-H2O was accompanied by the deposition of its higher oxidation state (H2O)RuII–RuIII(OH), as evidenced with cyclic voltammetry, SEM and XPS. The IPCE and spectro-electrochemistry studies supported by TD-DFT calculations revealed the visible light harvesting ability of 1-H2O and 2-H2O in solution and the subsequent electron injection into the conduction band of the nanoITOs, enhanced in 2-H2O via a plausible chelating effect.

Nature of the abnormally high photocurrent relaxation time in the a-Ga2O3-based Schottky diodes

Ga2O3 is an ultra-wideband material with excellent optical characteristics. It is a promising material for power applications and optoelectronics because of its high electrical breakdown voltage and radiation hardness. It is optically transparent for visible light and UVA but UVC-sensitive. One of the main disadvantages of this material is the anomalous slow photoeffect: photoconductivity rise and decay characteristic times can be more than hundreds of seconds long. This "slow" photoconductivity effect severely limits the utilisation of the Ga2O3-based devices. The aim of this work is the investigation of the nature of this effect. The results of the photoinduced current rise and decay under 530 nm and 259 nm LED are measured in the HVPE-grown α-Ga2O3-based Schottky diode. Upon UV-illumination the photocurrent rise consists of three parallel processes: fast signal growth, slow growth and very slow decay with characteristic times near 70 ms, 40 s and 300 s respectively. Subsequent 530 nm LED illumination resulted in photoinduced current rise consisting of two mechanisms with characterisatic times 130 ms and 40 s on which a very slow decrease of the photocurrent amplitude with characteristic time of 1500 s was superimposed. 530 nm illumination stimulates this process. Protoinduced current relaxation analysis shows the presence of the deep levels with energies (EC - 0.17 eV). It is suggested that extremely slow relaxations can be associated with potential fluctuations near the Schottky barrier.

Impact of Y2O3 Nanosheets on the Microstructural Characteristics of Alq3 Prepared via the Co-precipitation Route for Enhancement of Photodiode Performance.

In the present study, tris-(8-hydroxyquinoline) aluminum (Alq3) and tris-(8-hydroxyquinoline) aluminum/yttrium oxide Alq3/Y2O3 were synthesized by a facile chemical route. The crystal structure, surface morphological nature, and particle size were identified by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) micrographs. Ag/Alq3/p-Si/Al and Ag/Alq3:Y2O3/p-Si/Al diodes were fabricated by the thermal evaporation technique and the electrical characteristics were evaluated from the I-V plots in dark and under illumination intensity. Thermionic emission theory, Cheung-Cheung, and Nord model have been applied to define the main electronic parameters like series resistance (Rs), barrier height (ϕb), and ideality factor (n). The hybrid Ag/Alq3:Y2O3/p-Si/Al diode revealed a nonideal behavior with high shunt resistance Rsh and good photocurrent sensitivity. The C/G-V analysis indicated that both C and G are strongly affected by the presence of trapped charge carriers at the interface states. The obtained results indicated that Rs was decreased whereas the carrier concentration (Na) was increased by loading Y2O3 nanosheets.

Arsenic-Doped CdSeTe Solar Cells Achieve World Record 22.3% Efficiency

For more than three decades, Cu has been critical to dope CdSeTe solar cells, form effective contacts, and maximize efficiency. At the same time, Cu defect chemistry has limited stability, carrier concentration, and further efficiency improvements. In this article, 22.3% world record efficiency is demonstrated without Cu by implementing As doping, which also improves stability, temperature coefficient, and energy yield. The efficiency crossing point of Group V technology relative to Cu has been driven by steady improvements in the open-circuit voltage. Here, the certified record cell reaches open-circuit voltage of 899 mV while retaining high photocurrent values of 31.4 mA/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ; the fill factor is relatively low at 78.9%. Coupling 80% fill factor with top open-circuit voltage values of 917 mV reported here offers a near-term path to 23% efficiency. Characterization indicates reducing recombination and improving activation provide viable paths to 25% efficiency.

Development of new co-sensitizer based squaraine dyes for enhancing the performance of DSSC

The conversion of near-infrared (NIR) light into electricity is a crucial goal for advancing the capabilities of dye-sensitized solar cells (DSSC). In order to achieve this, two novel squaraine dyes, namely SQI-P and SQI-H, were synthesized and employed as NIR sensitizers in DSSC. These dyes were constructed with a conjugated indoline donor on both sides of the squaraine core, and a long pendant group on the N-position. The strongly donating indoline with phenyl bis-carboxylic anchor groups located in the N-position resulted in a high molar extinction coefficient and a broad absorption spectrum that extended into the NIR region. The experimental results showed that SQI-P/SQI-H sensitizer exhibits strong absorption in the NIR region, improved electron injection efficiency, and excellent photostability. After optimizing the co-sensitized DSSC, the combination of the NIR-absorbing squaraine based-indoline with SQI-P produced a high photocurrent output of 22.3 mA/cm2 at an efficiency of 4.8%. This achievement represents a breakthrough for DSSCs and paves the way for a more efficient future of DSSCs in the NIR region.

Reduced graphene oxide-functionalized zinc oxide nanorods as promising nanocomposites for white light emitting diodes and reliable UV photodetection devices

We present a breakthrough in the development of novel nanocomposites based on reduced graphene oxide (RGO)-functionalized zinc oxide (ZnO) nanorods that hold exceptional promise for their use in white light emitting diodes (LEDs) and reliable UV photodetection. The nanorods had a pristine hexagonal wurtzite structure, as confirmed by XRD analysis. SEM images revealed sandwich-like nanocomposites with ZnO nanorods coated in reduced graphene oxide and embedded between two layers of RGO. The study also confirmed the hybridization and interactions between the layers using Raman measurements. The resulting nanocomposites displayed a lower band gap energy than ZnO and exhibited unique photoluminescence spectra with a white PL light. The photodetector based on RGO/ZnO/RGO sandwich structures demonstrated exceptional photoresponse, with higher photocurrent under UV illumination, making it highly promising for a wide range of optoelectronic applications. Overall, this study offers a novel and powerful approach to create nanocomposite structures with enhanced optical characteristics.

High photocurrent performance of nebulizer sprayed Bi2S3 thin films by a novel Cu-La doping strategy

Nowadays, chalcogenide-based thin layers are proving a promising light-absorbing material with low cost and are technologically suitable for light to current conversion applications. In this study, for the first time, pristine Bi2S3, Bi2S3:Cu2%, Bi2S3:La2%, and Bi2S3:Cu2%:La2% thin films were prepared by nebulizer spray pyrolysis technique on a glass substrate at 300 °C. The obtained XRD pattern confirms the orthorhombic structure of Bi2S3 and possesses a maximum crystallite size of 38 nm for Bi2S3:Cu: La co-doped sample. Images taken with a FESEM analysis showed the unformed distribution of round shaped grains without any cracks and co-doping leads to the development of slight cluster formation. The optical absorbance spectra of the thin films were observed from the wavelength of 350 nm to 1000 nm, and the co doping process highly strengthen the optical absorbance, which is prerequisite for an efficient photodetector. A lower band gap value of 1.7 eV is achieved for Bi2S3: Cu: La thin film. From PL studies, defect emission bands around ∼325 and 525 nm related to band edge emission and sulfur vacancies are obtained. Further, UV photosensing properties of each sample were evaluated. Commendable performance with maximum responsivity (1.24 × 10−1 AW−1), detectivity (1.13 × 1010 Jones), and EQE (40%) were achieved for Bi2S3:Cu:La-sample. The enhanced figures-of-merit are attributed large crystalline size, good crystallinity, lower bandgap and crack free surface. The photo sensing results may widen the field of photosensing application.

Dimerized Small-Molecular Acceptor Enables the Organic Bulk-Heterojunction Layer with High Thermal Stability.

Incorporation of a non-fullerene acceptor (NFA) into an organic bulk-heterojunction currently has realized the extendable spectral response and high photocurrent generation in organic photodiodes. However, to allow these organic materials to be industrially commercialized, the thermal stability which enables the materials to survive under the process integration and operation needs to be considered. Generally, NFA small molecules showed high crystallinity, which aggregated through heating and led to the poor thermal stability. To tackle the thermal stability issue of highly efficient NFAs, two IDIC-based NFA dimers─IDIC-T Dimer and IDIC-TT Dimer─were designed, synthesized, and characterized; the thermal stability of the BHJ layer incorporating these dimer molecules was evaluated and compared with that of the BHJ layer using the monomer, IDIC-4Cl, as acceptors. Eventually, a power conversion efficiency of 9.44% was achieved for organic photovoltaic devices based on the NFA dimer. The dimers also showed remarkable thermal stability than the IDIC-4Cl monomer, which provided a promising direction for the polymer/small-molecule system in organic photodiodes for industrial practicability.

TiO2 nanostructures synthesized by electrochemical anodization in green protic ionic liquids for photoelectrochemical applications

This work studies the influence of the 2-hydroxyethylammonium acetate (2-HEAA) ionic liquid (IL) as an electrolyte in the electrochemical anodization of titanium for the synthesis of nanostructures for photoelectrochemical water splitting. Different 2-HEAA IL concentrations were used ranging from 0 to 4% v/v (IL-0 to IL-4) in electrolytes containing NH4F, water and ethylene glycol. Morphological, structural and electrochemical characterization of the nanostructures was carried out by means of field emission scanning electron microscopy (FE-SEM), high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), electrochemical impedance spectroscopy (EIS), and Mott-Schottky (MS) analysis. Additionally, photoelectrochemical tests were carried out in order to evaluate the efficiency of these materials as catalysts for water splitting applications. According to the obtained results, the electrolyte used for electrochemical anodization should contain little amount of NH4F (0.05 M) in order to obtain efficient nanostructures for photoelectrochemical purposes. However, small concentrations of IL (IL-0.25) resulted in nanostructures with higher photocurrents than doubling the NH4F concentration to 0.1 M. Therefore, the IL addition contributes to a more sustainable electrolyte formulation. The best photoelectrochemical response for water splitting processes was obtained for the nanostructures anodized with 1% v/v of 2-HEAA IL (IL-1) due to their high surface/area (higher pore diameters, smaller nanotubes wall thickness and higher nanotubes lengths), better crystallinity and electrochemical response, showing photocurrents more than 100% higher than the ones obtained for the nanotubes anodized without IL.

47‐1: Ambipolar Gap‐type a‐Si‐TFT Circuit Applied for a Color Ambient Light Sensor

In this paper, we proposed ambient light sensor (ALS) and color temperature sensor (CTS) circuit integrated in the edge of LCD display panel. The designed circuit is based on the thin film transistor (TFT) technology, the photo TFT can produce high photo current under light for sensor realizing ambient light from 0~50000Lux. Also, CTS circuit are based on ALS circuit but covered with color filter. The result shows that CTS can discriminate different color temperature in ambient light. The biggest advantage of this sensor is that it is compatible with TFT process in manufacturing, and it is small in size and high in efficiency. It has the potential to replace photodiode sensors.

A silver nanoparticle (AgNP)-loaded Bi2Se3 topological insulator p-n heterojunction photodiode for a near-infrared (NIR) photodetector

Near-infrared (NIR) photons are expanding advanced applications in optoelectronics. However, while 2D materials like graphene offer an attractive route for NIR photodetection, the alternative for high-performance NIR detection is still evolving. Hence, solution-processed n-Bi2Se3 /p-Si-based 2D heterojunction photodiodes have been fabricated here and used for high-performance NIR detection. Further, we report high photoresponsivity of 248 mA W−1 at 1100 nm, high external quantum efficiency of 22, 23 and 28% for Ag-loaded (at 5, 7.5 and 10%) Bi2Se3 and good stability. The chemical states of Bi2Se3 and Ag are detected using the core-level spectra of x-ray photoelectron spectroscopy. Photoresponse I–V characteristics are investigated under both dark and illumination; the high photocurrent achieved for Ag-loaded Bi2Se3 and the increase in the forward photocurrent under both dark and bright conditions are reported. The temporal photoresponse curve confirms the good stability (photoswitching behavior) and reproducibility with a response time of 0.74 s and a decay time of 0.18 s. Therefore, these unique performance and device parameters of a manufactured photodiode strongly recommend as a potential heterojunction photodiode for an NIR photodetector.

NaBiS2 decorated polysaccharide sponges for adsorption–photocatalytic degradation of dye under visible light illumination

Dye is emissions aggravating aquatic ecosystem pollution, and photocatalysis is considered the most appealing option to remove dyes by degradation. However, the current photocatalysts suffer from agglomeration, large bandgaps, high mass transfer resistance, and high operation cost. Herein, we present a facile hydrothermally induced phase separation and in situ synthesis strategy for fabrication of sodium bismuth sulfide (NaBiS2)-decorated chitosan/cellulose sponges (NaBiCCSs). The NaBiCCSs demonstrate unique polysaccharide cellular structure (150–500 μm), uniformly immobilized NaBiS2 nanoparticles (70–90 nm), narrow bandgap (1.18 eV), high photocurrent (0.74 μA/cm2), and outstanding compressibility. Benefiting from the characteristics and the high affinity to dyes, the NaBiCCSs provide innovative synergistic adsorption–photocatalytic degradation model for dye removal, attaining a superior methylene blue removal rate of 98.38 % under visible light illumination and offering good reusability. This study offers a sustainable technical solution for dye contaminant removal.

NiCo2S4@ZnIn2S4-Assisted All-in-One Self-Powered electrochemical device for ultrasensitive detection and degradation of AFB1

Self-powered sensors are easy to be integrated and miniaturized without power supply, providing an attractive way to construct smart, portable and implantable device. However, it is challenging to realize practical application especially for food safety problems due to the low energy conversion efficiency and the degradation difficulty of toxins. Herein, a new all-in-one photocatalytic self-powered electrochemical device (SPED) was proposed for the first time to achieve sensitive detection and efficient degradation of aflatoxin B1 (AFB1) by the integration of photocatalytic fuel cell with photocatalytic degradation. NiCo2S4@ZnIn2S4 (NCS@ZIS) heterojunction was used as photoanode material with a high photocurrent of 13.7 μA, improving the photoelectric conversion efficiency greatly. By combining with photocathode, the output power of the SPED was greatly boosted to 467.4 mV, which realized AFB1 detection ranging from 0.001 ng/mL to 1000 ng/mL with a low detection limit of 0.17 pg/mL. In addition, owing to the photocatalysis of NCS@ZIS heterojunction as well as the drive of voltage difference between anode and cathode, the SPED showed a high degradation efficiency up to 81.62 % within 120 min. The successful construction of the all-in-one SPED achieved ultrasensitive detection and degradation of AFB1, demonstrating a great promising application in food security and environmental monitoring areas.

Dual metallic-based plasmonic back reflector to broaden the absorption spectra of a thin film amorphous silicon solar cell

Here, to obtain high efficiency in a thin film amorphous silicon solar cell, a dual metallic plasmonic back reflector was investigated. The designed dual metal plasmonic back reflector can improve the photocurrent and hence the efficiency. At first, a double layer SiO 2/Si3N4 as the antireflection (AR) was analyzed. The efficiencies of 8.74%, 11.38%, 12.53%, and 13.04% are obtained for a cell without AR, with SiO2, Si3N4, and SiO2/SiN 4 AR layers, respectively. A disk-ring and dual rings-based Ni and Ti-based plasmonic back reflector were designed. The study was carried out by a 3D finite difference time domain method and the optimized parameters were calculated to obtain higher efficiencies. Finally, a relatively higher photocurrent and conversion efficiency of 19.86mA/cm2 and 15.65% were achieved for the optimized structure with a dual Ni rings back reflector, respectively. Because of the importance of amorphous silicon solar cells due to the cost problem of crystalline silicon, here, the simulation steps present a valuable road map to design a novel plasmonic thin-film amorphous silicon solar cell.

Multifunctional and High‐Performance FAPBI3 Quantum Dots/Graphene UV Photodetectors by the Modulation of Photoconductivity

AbstractLow‐dimensional devices with different photoconductive effects attract much attention in optoelectronics. In this work, negative photoconductivity (NPC) monolayer graphene photodetectors are fabricated by chemical vapor deposition (CVD), and a positive photoconductivity (PPC) photodetector is realized by decorating perovskite FAPbI3 quantum dots prepared by a simple and cost‐effective non‐polar solvent synthesis method on a graphene surface. The graphene‐based photodetector exhibits an NPC characteristic, which is attributed to the absorption and desorption of water molecules on the graphene surface. The responsivity of the photodetector with an NPC characteristic is −0.86 A W−1 under intense ultraviolet light irradiation, and the detectivity is −2.45 × 109 Jones. The FAPbI3 quantum dots/graphene photodetector with a PPC feature has a responsivity of 8.03 A W−1 and a detectivity of 1.89 × 1010 Jones under the irradiation of ultraviolet light of 365 nm and 55.3 mW cm−2 intensity. Due to the intense light absorption of perovskite combined with the extremely high mobility of graphene, photodetectors have high exciton separation and photocurrents when the devices are irradiated by ultraviolet light. Individual photodetectors are successfully created with NPC and PPC effects; the critical analysis for the different photoconductive mechanisms is provided, which will benefit the development of future multifunctional systems.

X‐Ray Nanoanalysis Revealing the Role of Electronically Active Passivation Layers in Perovskite X‐Ray film Detectors

AbstractX‐ray direct detectors based on hybrid lead‐halide perovskite have seen a dramatic increase of interest in the last years. A rush for the achievement of high performing devices drives the scientific community. In this context, several photoconductor sensors employ functional layers to increase the gain effect, but the full comprehension of the mechanism is still lacking. Here, X‐ray nanoanalysis is used, performed by simultaneous acquisition of X‐ray Fluorescence and X‐ray Beam Induced Current maps, to investigate at the nanoscale level the role of [6,6]‐phenyl‐C61‐butyric acid methyl ester fullerene (PCBM) molecules when interacting with MAPbI3 polycrystalline thin films acting as photo‐conductors in X‐ray detectors. At the device‐scale level it shows that the addition of PCBM enhances the X‐ray sensitivity by four times. At the nanoscale level how the perovskite grain boundaries act as high photocurrent generation centers is demonstrated. The addition of the PCBM increases the photocurrent generation, as the macroscopic performance does, and the charge collection becomes uniform over the full crystallite volume. The results clarify the role of grain boundaries and charge selecting layers and establish the X‐ray nanoanalysis techniques as a powerful tool to investigate charge transport and collection in perovskite films.

Exploring the photo-induced charge transfer behavior of Cs3Bi2I9 and BiI3 using in-situ surface photovoltage spectroscopy

This letter compared the photo-induced charge carrier properties of Cs3Bi2I9 and BiI3 deposited on conductive glass using surface photovoltage spectroscopy. The study showed that the higher photocurrent in BiI3 cannot be solely attributed to its extended absorbance range. The charge transfer capability of the photoactive layer was found to be a critical factor in determining photocurrent. The study also revealed better transfer of photo-induced electron-hole pairs and higher surface electron concentration in BiI3. Additionally, light-chopping-frequency-dependent surface photovoltage measurements showed that photogenerated charge carriers can be separated more effectively and in a shorter illumination period in BiI3 than in Cs3Bi2I9.

TiS3 Nanoribbons: A Novel Material for Ultra-Sensitive Photodetection across Extreme Temperature Ranges.

Photodetectors that can operate over a wide range of temperatures, from cryogenic to elevated temperatures, are crucial for a variety of modern scientific fields, including aerospace, high-energy science, and astro-particle science. In this study, we investigate the temperature-dependent photodetection properties of titanium trisulfide (TiS3)- in order to develop high-performance photodetectors that can operate across a wide range of temperatures (77 K-543 K). We fabricate a solid-state photodetector using the dielectrophoresis technique, which demonstrates a quick response (response/recovery time ~0.093 s) and high performance over a wide range of temperatures. Specifically, the photodetector exhibits a very high photocurrent (6.95 × 10-5 A), photoresponsivity (1.624 × 108 A/W), quantum efficiency (3.3 × 108 A/W·nm), and detectivity (4.328 × 1015 Jones) for a 617 nm wavelength of light with a very weak intensity (~1.0 × 10-5 W/cm2). The developed photodetector also shows a very high device ON/OFF ratio (~32). Prior to fabrication, the TiS3 nanoribbons were synthesized using the chemical vapor technique and characterized according to their morphology, structure, stability, and electronic and optoelectronic properties; this was performed using scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, X-ray diffraction (XRD), thermogravimetric analysis (TGA), and a UV-Visible-NIR spectrophotometer. We anticipate that this novel solid-state photodetector will have broad applications in modern optoelectronic devices.

Facile synthesis of Bi2WO6/Bi2MoO6 Z-scheme heterojunction for dye degradation and Cr(VI) reduction

Dyeing wastewater has been one of the severe pollutant crises along the textile industry development, and the design of effective photocatalysts is the attractive strategy for wastewater remediation. Herein, Bi2WO6/Bi2MoO6 microspheres with the high surface area of 12.16 m2/g were prepared by the solvothermal synthesis method, and the hybrid photocatalyst exhibited outstanding solar absorption, photoelectric conversion and photocatalytic performances. The photoelectric tests indicated that the sample photoelectrode exhibite high transient visible light-driven photocurrent value (1.91 μA/cm2) and low interface resistance. The photocatalytic rate constants for rhodamine B (RhB), methylene blue (MB) photodegradation achieved 1.65 × 10-2 min−1 and 3.78 × 10-2 min−1. The main active species for dye photodegradation were O2 radicals, and the preparation and photocatalytic mechanisms were proposed. Furthermore, the as-prepared photocatalyst also showed high photoremoval of Cr(VI) under visible light irradiation, and the high photocatalytic efficiency (68.57%) was obtained after 160 min irradiation. The excellent photoelectrochemical performance was mainly ascribed to the outstanding photoelectron separation and transportation from Z-scheme heterojunction structure construction. The investigation about Bi2WO6/Bi2MoO6 photocatalysts would provide a feasible route for novel photocatalyst design toward photocatalytic dyeing wastewater purification.

Two Bulk-Heterojunctions Made of Blended Hybrid Nanocomposites for High-Performance Broadband, Self-Driven Photodetectors.

Heterojunctions based on low dimensional semiconducting materials are one of the most promising alternatives for next-generation optoelectronic devices. By choosing different dopants in high-quality semiconducting nanomaterials, p-n junctions can be realized with tailored energy band alignments. Also, p-n bulk-heterojunctions (BHJs) based photodetectors have shown high detectivity because of the suppressed dark current and high photocurrent, which are due to the larger built-in electric potential within the depletion region and can significantly improve the quantum efficiency by reducing the carriers' recombination. In this work, PbSe quantum dots (QDs) blended with ZnO nanocrystals (NCs) were used as the n-type layer, while CsPbBr3 NCs doped with P3HT were used as the p-type layer; as a result, a p-n BHJ was formed with a strong built-in electric field. Consequently, such a kind of p-n BHJ photodetector ITO/ZnO/PbSe:ZnO/CsPbBr3:P3HT/P3HT/Au showed a high ON/OFF current ratio of 105 with a photoresponsivity of 1.4 A/W and specific detectivity of 6.59 × 1014 Jones under 0.1 mW/cm2 532 nm illumination in self-driven mode. Moreover, the simulation performed by TCAD also agrees well with our experimental results, and the underlying physical mechanism for enhanced performance is discussed in detail for this type of p-n BHJ photodetector.