Inorganic Heterojunction Research Articles

Low Leakage Current by Solution Processed PTAA-ZnO Transparent Hybrid Hetero-Junction Device

In this work solution processed novel poly-triarylamine (PTAA) organic p-type active layer on inorganic n-ZnO device transparency and electrical properties are investigated under illumination. Low cost organic–inorganic transparent hybrid hetero-junction (HHJ) is a promising candidate for next-generation photovoltaic applications. Greater band gap organic material window layer while inorganic material’s higher thermal stability as HHJ is suitable for detection and photovoltaic applications. However, hetero-interface defects associated leakage current is the key issue of undermining large-area device electrical performance. Hetero-interface defect associated carriers optical absorption limits transparency whereas leakage current density is reliant on physical property and band barrier effect. It is demanded to investigate hetero-device physical stuff and band barrier effect on electrical properties. Novel PTAA is deposited on RF-sputtered inorganic n-ZnO/ITO/glass substrate by spin-coating method. 100 and 60 nm PTAA thin films are deposited with 1000 and 2000 revolution per minute (rpm) growth sequence, respectively. PTAA as a transparent p-emitter is shown to absorb incident light beyond visible band, thereby it has promoted excitonic effect. Device I–V characterization carried out at different annealing temperatures and applied voltage. Suitable annealing condition leakage current is shown to reduce nearly 10−4 A/cm2 and at higher applied field the greater rectifying I(+)/I(−) ratio is realized. Grain size is shown to increase with annealing effect however; leakage current is remained almost independent of grain size.

Synthesis, structure and photoelectric properties of selenide composites with in situ constructed Sb2Se3/NaSbSe2 heterojunction

Inorganic semiconductor heterojunctions have attracted extensive attention for technological applications owing to interface phenomena. In this work, selenide composites with in situ constructed Sb2Se3/NaSbSe2 heterojunctions with similar band gap width have been synthesized by conventional melt-quenching method. The microstructure and photoelectric properties of the composites were investigated at different NaSbSe2 contents. The study revealed that NaSbSe2 content has direct influences on the photoelectric performance of the composites by modifying the heterojunction size and the grain boundary resistance, as evidenced by scanning electron microscopy and impedance spectroscopy, respectively. The photocurrent density of Sb2Se3 with 2.5 and 5 mol% NaSbSe2 was approximately 180 times larger than that of the pure Sb2Se3 at a bias voltage of -1.5 V and under an illumination of 7 mW/cm2, due to an effective separation of photogenerated carriers through the interface electric field. Additionally, the composites exhibited an excellent stability even in 0.5 M LiClO4 aqueous electrolyte.

Passive Filters for Nonvolatile Storage Based on Capacitive-Coupled Memristive Effects in Nanolayered Organic–Inorganic Heterojunction Devices

It is well known that the reprogrammable device is one of the important needs for circuit design. In this paper, nanolayered TiO2 and maple leaves (ML) are combined to form a functional layer (TiO2...

Structural and Morphological Characteristics of Organic and Inorganic Blend Heterojunction NiPcTs/CdS

In the present study NiPcTs, CdS thin films, and Blends of NiPcTs/CdS were prepared with 1:2 content mixing ratio of NiPcTs to CdS solutions. Cadmium chloride and thiourea were used as the essential materials for deposition CdS thin films while using organic powder of NiPcTs to deposit NiPcTs nanostructure films. The spin-coating technique was employed to fabricate the NiPcTs, CdS films, and NiPcTs-CdS blend. Structural properties of films have been investigated via X-Ray diffraction, and show that thin films of NiPcTs, and CdS have monoclinic and polycrystalline hexagonal structure respectively while the blend has two polycrystalline structure with cubic and hexagonal phases. Atomic force microscope (AFM) confirmed that the surface of all samples are quite smooth and they have comprised of spherical numerous nanoparticles with diameter less than 70 nm. Scanning Electron Microscopy (SEM), and energy dispersive spectroscopy (EDS)analyzer has been achieved to determine the chemical composition of the molecular materials, which exhibit the existence of all essential elements of thin films and blend heterojunction (BHJ) of NiPcTs -CdS. The preparation of chemical solutions, deposition of NiPcTs, CdS thin films and the blend heterojunction BHJ of NiPcTs–CdS have been characterized.

Performance improvement of organic resistive memories by exploiting synergistic layered nanohybrid dispersed polymer composites

Functionalized layered nanohybrid materials have been thoroughly explored in numerous practical applications including photocatalysis, supercapacitors, and sensors, and have inherent potential to excel in the field of organic resistive random access memory devices as well. Herein, we report an efficient, facile, and cost-effective in situ synthesis route to prepare a layered nanohybrid by grafting cadmium sulfide (CdS) nanorods with exfoliated graphene oxide (GOs) sheets via the one-step hydrothermal functionalization technique. Such a nanohybrid material displays advantageous characteristics possessed by them due to the formation of organic–inorganic heterojunctions at their interface. Sandwiched devices, with a configuration of ITO/reduced graphene oxide–CdS/poly-methyl methacrylate (PMMA)/Al, are fabricated by dispersing different wt. % of the layered nanohybrid in a poly-methyl methacrylate (PMMA) matrix. Detailed current density vs voltage (J–V) studies exhibit excellent bipolar resistive switching characteristics reaching a very low set voltage of ∼−0.48V, high current ION/IOFF ratios of ∼106, and ultralow set/reset power densities of ∼10−8/10−6W/cm2 for devices containing 0.4 wt. % nanohybrid nanofillers. Partial reduction of GOs and the formation of heterojunctions during the synthesis process undoubtedly boost the resistive memory performances resulting from the synergistic effect in layered nanohybrid materials. The fabricated devices have been subjected to various analyses in order to test their stability, repeatability, and reliability, all of which have been found to display encouraging results.

A self-powered solar-blind photodetector with largeVocenhancing performance based on the PEDOT:PSS/Ga2O3organic–inorganic hybrid heterojunction

A self-powered solar-blind photodetector with largeVocenhancing performance is constructed on the PEDOT:PSS/Ga2O3hybrid heterojunction.

Direct observation of charge transfer between molecular heterojunctions based on inorganic semiconductor clusters.

A deep understanding of the dynamics of photogenerated charge carriers is extremely important for promoting their germination in semiconductors to enhance the efficiency of solar energy conversion. In contrast to that of organic molecular heterojunctions (which are widely employed in organic solar cells), the charge transfer dynamics of purely inorganic molecular heterojunctions remains unexplored. Herein, we reveal the dynamics of charge transfer between inorganic semiconductor molecular heteroclusters by selecting a group of open-framework metal chalcogenides as unique structure models constructed from supertetrahedral T3-InS ([In10S20]) and T4-MInS ([M4In16S35], M = Mn or Fe) clusters. The staggered band gap alignment in T3-T4-MInS molecular heterojunctions enables the photogenerated charge carriers to be directionally transferred from T3-InS clusters to adjacent T4-MInS clusters upon irradiation or application of an external electric field. The simultaneous independence of and interactions between such two heteroclusters are investigated by theoretical calculations, steady- and transient-state absorption/photoluminescence spectroscopy, and surface photovoltage analysis. Moreover, the dynamics of cluster-to-cluster-to-dopant photogenerated charge transfer is deliberately elucidated. Thus, this work demonstrates the direct observation of charge transfer between molecular heterojunctions based on purely inorganic semiconductor clusters and is expected to promote the development of cluster-based semiconductors for solar cells.

The anchored location of CdS on SiC via organosilane for effective heterogeneous interface design in photocatalysis

This work demonstrates a new approach to construct a heterogeneous junction by means of the periodic lattice distribution of semiconductor atoms. The organosilane was applied as an anchored coupling agent to connect the semiconductors at both ends, one of which connects SiC and the other connects CdS, and the SiC/M/CdS heterogeneous junction was established. The photocatalytic hydrogen evolution ability of this heterojunction was three times as much as the traditional SiC/CdS composite under visible light. Meanwhile, the uniform interface distribution, prolonged charge-carrier lifetime and minor electron–hole recombination were achieved. The results provide new insights into interface design and offer an indepth understanding with respect to organic–inorganic heterojunction configuration in photocatalysis.

Photocatalytic dye degradation and hydrogen production activity of Ag3PO4/g-C3N4 nanocatalyst

Recently, photocatalysts have received increasing attention owing to their potential to resolve issues regarding the environment and alternative sources of energy. Here, highly effective visible-light-driven organic–inorganic hybrid heterojunction graphitic carbon nitride–silver phosphate nanocomposite (GCN–Ag3PO4 NCs) were synthesized via the hydrothermal method. The synthesized photocatalyst was characterized by X-ray diffraction, Fourier transform infrared, X-ray photoelectron spectroscopy, and UV–Vis diffuse reflectance spectroscopies, scanning electron microscopy and transmission electron microscopy, and subsequently utilized for photocatalytic dye degradation and hydrogen production. The GCN–Ag3PO4 NCs exhibit excellent photocatalytic activity for methylene blue degradation under solar simulator visible light, with a hydrogen production activity higher than that of pristine Ag3PO4. The hydrogen production rate of GCN–Ag3PO4 NCs is 44.5 times higher than that of Ag3PO4. Therefore, GCN–Ag3PO4 NCs are promising as effective photocatalysts for environmental protection.

Electrical and Photovoltaic Responses of an Au/Coumarin 337/n-Si/Sb-Au Hybrid Organic–Inorganic Solar Cell

Thin films of coumarin 337 (C-337) dye were fabricated on n-type silicon (111) wafer using a high-vacuum thermal evaporation technique. Investigation of their structure using x-ray diffraction analysis and scanning electron microscopy revealed that the pristine C-337 films had sphere-shaped nanostructure. The absorbance, transmittance, and reflectance of the C-337 films were measured spectrophotometrically. Tauc’s method revealed an indirect allowed-type optical transition for these films with an optical band gap of 1.59 eV assisted by phonons of 52 meV. Hybrid organic–inorganic heterojunction solar cells based on C-337 were deposited on n-type single-crystal silicon wafer. Many aspects of the electrical parameters of the Au/C-337/n-Si/Sb-Au heterojunction solar cells were studied under dark condition based on their capacitance–voltage, conductance–voltage, and current–voltage characteristics at different frequencies (100 kHz to 1 MHz). The Nyquist diagram of the solar cell was recorded at various frequencies. Furthermore, the illuminated current–voltage and phototransient characteristics of the cell were also measured and used to evaluate the photovoltaic performance of the device. Under illumination intensity of 90 mW/cm2, the solar cell showed good photovoltaic behavior with short-circuit current, open-circuit voltage, fill factor, and power conversion efficiency of 5.42 mA, 0.55 V, 0.59, and 4.39%, respectively. The photovoltaic and phototransient properties of the device indicate that it could be applied as both a solar cell and a linear dynamic range optoelectronic switching sensor.

Long‐Range Ordered Crystals of 3D Inorganic–Organic Heterojunctions via Colloidal Lithography

AbstractColloidal lithography (CL) has evolved as an alternative to conventional photo‐ and electron‐beam lithography to pattern surfaces with nanometer range resolution. As CL offers substrate‐independent precise positioning and patterning of nanomaterials as long‐range ordered crystals, this has seen new opportunities in optoelectronics. Herein, the scope of CL is expanded to fabricate for the first time, 3D organic–inorganic heterojunction photocatalysts with well‐controlled spacing and coverage density. To achieve this, monodisperse polystyrene (PS) beads of different sizes are used as colloidal masks on a ZnO substrate. Electron beam assisted silver deposition onto these PS masks, and subsequent removal of PS lead to the formation of patterns of silver nanostars on the ZnO thin film. The solid–vapor reaction of silver nanostars with a metal‐coordinating charge‐transfer complex of 7,7,8,8‐tetracyanoquinodimethane (TCNQ) allows spontaneous conversion of Ag nanostars to the large aspect ratio nanowires of metal–organic AgTCNQ semiconductors. This strategy, combining the strengths of CL with high electron affinity of TCNQ molecules allows facile fabrication of long‐range patterns of the heterojunctions of organic (AgTCNQ) and inorganic (ZnO) semiconductors. These surface‐supported 3D heterojunctions act as outstanding photocatalysts through their ability to efficiently separate the electron–hole pairs and thus increasing the electron–hole life times.

Enhanced organic−inorganic heterojunction of polypyrrole@Bi2WO6: Fabrication and application for sensitive photoelectrochemical immunoassay of creatine kinase-MB

In this report, enhanced organic−inorganic heterojunction of polypyrrole@Bi2WO6 was fabricated and applied for sensitive photoelectrochemical (PEC) immunoassay of creatine kinase-MB (CK-MB). Specifically, heterostructured polypyrrole@Bi2WO6 photoelectrode was prepared and sandwich immunorecognition were integrated for the CK-MB immunoassay. In the detection, with the aid of alkaline phosphate (ALP)-induced biocatalytic precipitation (BCP), the precipitation-dependent suppression of the photocurrent can be recorded due to the impediment of the interfacial mass and electron transfer. On the basis of target-controlled BCP formation, a novel PEC immunoassay could be developed for the sensitive and specific CK-MB detection. This work manifested the great potential of polypyrrole@Bi2WO6 heterojunction as a novel platform for PEC bioanalysis development and also a PEC method for CK-MB detection. This work is expected to stimulate more interest in the design and implementation of numerous other organic−inorganic heterojunction for advanced PEC bioanalysis development.

Ultrahigh EQE (15%) Solar‐Blind UV Photovoltaic Detector with Organic–Inorganic Heterojunction via Dual Built‐In Fields Enhanced Photogenerated Carrier Separation Efficiency Mechanism

AbstractA new strategy of constructing an additional heterojunction on the surface of epitaxially grown Ga2O3 film with a distorted lattice is proposed to solve the problem of low external quantum efficiency (EQE) in traditional Ga2O3 heterojunction photovoltaic devices. Experimentally, an organic–inorganic hybrid poly(3,4‐ethylenedioxythiophene):polystyrene sulfonate/Ga2O3/p‐type Si solar‐blind ultraviolet (SBUV) photovoltaic detector is constructed to achieve an ultrahigh EQE of ≈15% at 0 V bias, which is 1–2 orders of magnitude higher than that of the Ga2O3 photovoltaic devices reported previously. Here, an enhanced mechanism of photogenerated carrier separation efficiency induced by dual built‐in fields is proposed to explain the high EQE of Ga2O3 SBUV photovoltaic devices. In addition, the organic–inorganic hybrid detector displays a high SBUV–visible rejection ratio (R255 nm/R405 nm of ≈450) and fast response speed (rise time of 60 ms and decay time of 88 ms). All these results indicate that the strategy proposed could provide reference for the fabrication of high‐performance Ga2O3 SBUV photovoltaic detectors.

THE ROLE OF Br AS DOPANT ON THE STRUCTURAL AND CHARGE TRANSPORT PROPERTIES IN CH3NH3PbI3−x−yBrxCly MIXED-HALIDE PEROVSKITE FOR HYBRID SOLAR CELLS

A series of CH3NH3PbI[Formula: see text]BrxCly mixed-halide perovskite were fabricated as light harvesters for organic–inorganic planar heterojunction perovskite solar cells (PSCs). This paper aimed at investigating the morphology and structural properties of Br doped mixed-halide perovskites and the influence on the corresponding photovoltaic performances. We found that Br incorporation in an I/Cl-based structure dramatically improved the charge transport within the perovskite layer. The average efficiency of the planar device was 13.6% with a minimal standard deviation of [Formula: see text] 1.53% and best efficiency as high as 15.13% was achieved. Moreover, the device showed superior stability over 20 days with little degradation [Formula: see text]9% when stored under ambient conditions, indicating the outstanding performances of planar heterojunction solar cells based on this material. The results highlight the crucial role of the Br doping on the performance of the PSCs and pave the way for further progress on this field.

A tungsten oxide–lutetium bisphthalocyanine n–p–n heterojunction: from nanomaterials to a new transducer for chemo-sensing

An organic–inorganic heterojunction with an n-type behavior to detect ammonia in a humid atmosphere.

Synthesis, Characterization, DFT Studies, and Photodiode Application of Azo-azomethine-Based Ligand and Its Transition-Metal Complexes

An azo-azomethine-based ligand (H2L) and its transition-metal complexes were prepared, and the electronic structure of the synthesized compounds obtained computationally using density functional theory at B3LYP/6-31G (d,p) level. Furthermore, organic–inorganic heterojunctions were fabricated by forming thin films of complexes of H2L and Co(II), Ni(II), and Pd(II) metal on n-Si substrate. The fundamental electrical parameters of the rectifying heterojunctions were identified based on current–voltage data obtained in the dark at room temperature. The photosensing properties of the devices were investigated under illumination at various intensities from 40 mW/cm2 to 100 mW/cm2. The results showed that the photoelectrical characteristics of the devices could be modified by the thin film of metal complex, with the best photosensing properties being obtained for the heterojunction based on compound 1.

Fabrication and performance evaluation of ultraviolet photodetector based on organic /inorganic heterojunction

Organic/inorganic ultraviolet photodetector was fabricated using thermal evaporation technique. Organic/inorganic heterojunction based on thermally evaporated copper (II) acetylacetonate thin film of thickness 200 nm deposited on an n-type silicon substrate is introduced. I–V characteristics of the fabricated heterojunction were investigated under UV illumination of intensity 65 mW/cm2. The diode parameters such as ideality factor, n, barrier height, ΦB, and reverse saturation current, Is, were determined using thermionic emission theory. The series resistance of the fabricated diode was determined using modified Nord's method. The estimated values of series resistance and barrier height of the diode were about 0.33 KΩ and 0.72 eV, respectively. The fabricated photodetector exhibited a responsivity and specific detectivity about 9 mA/W and 4.6 × 109 Jones, respectively. The response behavior of the fabricated photodetector was analyzed through ON-OFF switching behavior. The estimated values of rise and fall time of the present architecture under UV illumination were about 199 ms and 154 ms, respectively. Finally, enhancing the photoresponsivity of the fabricated photodetector, post-deposition plasma treatment process was employed. A remarkable modification of the device performance was noticed as a result of plasma treatment. These modifications are representative in a decrease of series resistance and an increase of photoresponsivity and specific detectivity. The process of plasma treatment achieved an increment of external quantum efficiency from 5.53% to 8.34% at −3.5 V under UV illumination.

Organic–Inorganic Heterojunctions toward High‐Performance Ambipolar Field‐Effect Transistor Applications

AbstractThis work reports on combination of organic–inorganic heterojunctions between amorphous indium–gallium–zinc oxide (a‐IGZO) and organic semiconductors for design of high‐performance ambipolar transistors. A vertically sequential layer device configuration that the organic small molecule dinaphtho‐thieno‐thiophene (DNTT) and dioctylbenzothieno[2,3‐b]benzothiophene (C8‐BTBT) are directly vacuum deposited on the surface of a‐IGZO without any interface modification is employed in ambipolar transistors. The ambipolar transistors based on C8‐BTBT/a‐IGZO featured with V‐shaped transfer curves exhibit an outstanding electrical performance with mobilities as high as 5.1 and 4.5 cm2 V−1 s−1 for electrons and holes, respectively. The formation of N‐type channel even if covered with several tens of nanometers thick small molecule film is clarified with the charge injection mechanisms based on both thermionic injection and/or tunneling transport processes. High‐performance ambipolar inverter with extremely large gain of 124 V/V is fabricated based on the C8‐BTBT/a‐IGZO ambipolar transistors. Moreover, a single‐transistor frequency doubler shows high spectral purity with 70% of the output energy at the doubling frequency of 2 kHz. The present work provides a strategy for manufacturing high‐performance ambipolar transistor with straightforward processing approaches, which may help deepen the understanding of ambipolar channel's working mechanisms and optimize the design procedures of logic electrical components.

Fabrication and characterization of silicon nanowires hybrid Solar cells: A Review

Nowadays hybrid (inorganic-organic) solar cells have become centre for attractive research for their comparatively low cost and fundamental research for prominent organic - inorganic hetero-junction. This review mainly aims to focus on the basic concepts of silicon nanowires (Si-NWs) hybrid solar cells including different fabrication and characterization procedures and the fundamental aspects on which solar cell works. Various techniques have been reported for the synthesis of Si-NWs such as CVD, Oxide assisted growth, Lithography and electro-less metal assisted chemical etching. A further discussion is made on the various characterization procedures such as SEM, TEM, XRD, XPS, UV-Vis, PL, FTIR, Raman and IV for both Si-NWs and the hybrid solar cell. Furthermore a comparison has also been made between various solar cells with the help of a table showing different Si-NWs hybrid solar cell and their efficiencies.

Metal oxide heterojunction (NiO/ZnO) prepared by low temperature solution growth for UV-photodetector and semi-transparent solar cell

Wide bandgap inorganic metal oxide heterojunctions p-NiO/n-ZnO have been prepared by two low temperature solution growth techniques. Namely, one-dimensional ZnO nanostructure arrays electrodeposited in a pulsed mode, and nanocrystalline NiO films synthesized via Successive Ionic Layer Adsorption and Reaction (SILAR). The crystal structure, morphology, and optical properties of NiO films and NiO/ZnO heterostructures were investigated both before and after annealing in air. The analysis of the dark current vs. voltage characteristics and temporal response curves of the NiO films and corresponding NiO/ZnO heterostructures have shown the promise of their use in the effective UV-photodetectors. Poor photovoltaic characteristics of the test samples on the base of obtained NiO/ZnO heterostructures probably associated with their not quite optimal design, and with too large series resistances and diode ideality factors of the manufactured p-NiO/n-ZnO heterojunctions, that will be corrected by scrutinizing the defects in the metal oxides and through the improvement of the NiO/ZnO heterostructure design. Solving these problems will provide the effective application of the wide bandgap metal oxide NiO/ZnO heterostructures prepared by low temperature solution growth in the UV-active semi-transparent solar cells.