Double Heterojunction Research Articles

Broadband photodetector based on Co3O4/ZnO/Si double heterojunctions: A morphological and optoelectronic study

The growing demand for efficient and cost-effective optoelectronic devices has motivated extensive research into advanced photodetector architectures. This work realizes a robust platform for broadband photodetection via architectural engineering of Co3O4/ZnO/Si double heterojunctions using facile chemical spray pyrolysis. Comprehensive materials and device characterization provides fundamental insights into the role of tailored morphology, band alignment engineering, and defect landscape in dictating device behavior. Aligned ZnO nanorods and fine-grained Co3O4 layers enable efficient light harvesting and charge transport. A triple bandgap structure stemming from the synergistic combination of the two oxides facilitates broadband spectral response from 400 to 1000 nm. Based on the optical properties, triple energy bandgap ranges have been observed, ZnO exhibits an energy bandgap ranging from 2.35 eV to 3.15 eV, while Co3O4 shows energy bandgaps in the range of 1.85 eV–2.23 eV and 1.35 eV–1.5 eV. The responsivity measurements show that Co3O4/ZnO/Si double-heterojunction device has the highest responsivity over a wide range, with distinct peaks at 480 nm and 950 nm, reaching values of 3.5 A/W and 4.5 A/W, respectively. Analysis of electrical transport characteristics and energy band diagrams elucidates the photogenerated carrier dynamics and photocurrent generation governed by strategic heterointerfaces. These fundamental insights into nanoscale interface and architecture engineering lay the foundation for custom-designing high performance metal oxide heterojunction photodetectors through facile and scalable spray pyrolysis technique.

Enhanced photocatalytic activity of BiOCl/BiOBr/SnS2 heterojunction using a superfine SnS2 and double S-scheme

Photocatalysis is a green approach to solving energy and environmental problems, and researchers are still pursuing high-performance photocatalysts. Although BiOX (X = Cl or Br) has a suitable bandgap and good stability, its photoresponse is mostly concentrated in the UV region. Conversely, SnS2 has a wide photoresponse range but exhibits perceptible photocorrosion and poor stability. To exploit the advantages of both BiOX and SnS2, this study hydrothermally synthesized and introduced superfine SnS2 (∼30 nm in size) into a BiOCl/BiOBr binary system to fabricate BiOCl/BiOBr/SnS2 composites. Subsequently, the degradation performance of these composites in a Rhodamine B solution under visible light was investigated. Results show that the BiOCl/BiOBr/SnS2 heterojunctions were successfully prepared and the composites exhibited the best photocatalytic performance with 6% mass fraction of SnS2 (BiOCl-to-BiOBr mol ratio = 1:1). The formation of a double S-schedule heterojunction between BiOCl/BiOBr and SnS2 not only accelerated charge separation and transfer but also broadened the photoresponse range and reduced photoelectron–hole recombination under full-spectrum irradiation. Loading a small narrow-bandgap photocatalyst onto a large photocatalyst provides an effective way to construct heterojunctions with excellent photocatalytic performance. The ternary photocatalyst presents a favorable photocatalytic stability, and its photodegradation rate is 4.6, 4.5 and 220.5 times that of BiOCl, BiOBr and SnS2, respectively.

An Effective Strategy for the Photocatalytic Elimination of Industrial Wastewaters Via MgFe-LDH/TiO2 Heterojunctions

Reactive dyes are presently the most common type of dye utilised by the garment sector to colour wool, cotton, and viscose-based clothing. By using the typical biological degradation & sediment absorb approaches, it is quite impossible to get rid of them. Thus reactive dye colors in the effluent are major environmental issues in recent times. In this work Reactive dye series has been choosen for the photocatalytic degradation studies over calcined form of TiO2 and MgFe-LDHcal nanocomposites (TiO2/MgFe-LDHcal). This work assesses, a detailed investigation of the photocatalytic degradation of the reactive class dyes Ca. Reactive green 19, Reactive red 120, Reactive blue 4 and Eosin Yellowish dye by layered double hydroxide (LDH) and TiO2 heterojunction (MgFe-LDHcal/TiO2). Here for the first time, photocatalytic application of the said heterojunction was investigated toward the degradation of the reactive dyes. As these dyes are cytotoxic, mutagenic, and inhibit certain mitochondrial functions and often are carcinogens. This heterojunction system degrades the reactive dyes in 1 hour of visible light irradiation. The said LDH heterojunction was characterised by powder XRD to confirm the phase and composite formation, Uv-Visible and PL spectra to know the optical activity of the material in presence of light. The size, interplanar spacing and morphology of the nanoparticles were inspected by HR-TEM analysis. All the batch experiments were carried out at room temperature, without any adjustment of pH, at the dye concentration varying from 20 to 50 mg/L. Furthermore, according to the rejuvenation study, the prepared LDH heterojunction system could potentially be put to use for a number of cycles.

Fabrication of a Z-scheme Bi2MoO6/NiFe layered double hydroxide heterojunction for the visible light-driven degradation of tetracycline antibiotics

Heterojunction catalysts offer promising potential for efficient and sustainable remediation of polluted environments. In this study, Z-scheme Bi2MoO6/NiFe layered double hydroxide (BMO/NiFe) heterojunction catalysts were synthesized using solvothermal process. The surface morphology, crystalline structure, and photochemical characteristics of the synthesized photocatalyst were analyzed by several spectroscopic and electron microscopy methods. BMO, NiFe and BMO/NiFe were efficiently utilized for tetracycline (TC) antibiotics degradation under visible light irradiation. The experimental findings suggest that the BMO/NiFe15 heterojunction catalyst greatly enhances the TC degradation rate to 95 % under 300 W visible light irradiation for 120 min. The rate constant of 0.0219 min−1 indicates a rapid degradation process following pseudo first-order kinetics. Furthermore, the effect of active free radicals, the recyclability of the catalyst and the photocatalytic degradation mechanism of TC were proposed. This novel method opens up possibilities for creating advanced photocatalysts, which can effectively degrade TC in water bodies, addressing the urgent need for its removal from aquatic environments. The present work serves as a primary pathway to design and develop efficient Bi2MoO6-based direct Z-scheme photocatalysts with promising applications in simultaneous wastewater degradation with hydrogen evolution.

Double Z-scheme in SnO2/SnS2/Cu2SnS3 heterojunction for photocatalytic reduction of CO2 to ethanol

Photocatalytic reduction of CO2 to chemical fuels enables a sustainable way of reducing carbon emissions but faces a high reduction potential due to the high stability of CO2 molecules. Here, we prepared a SnO2/SnS2/Cu2SnS3 double Z-scheme heterojunction photocatalyst, in which SnO2, SnS2, and Cu2SnS3 absorb ultraviolet, visible, and near-infrared light, respectively. Based on the comprehensive analysis of in-situ X-ray photoelectron spectroscopy and photo(chemical) characterizations, we find that the photogenerated electrons would transfer from SnO2 to SnS2 to Cu2SnS3. The optimized SnO2/SnS2/Cu2SnS3–0.3 double Z-scheme heterojunction could achieve 28.44 µmol g–1 h–1 ethanol yield and 92% selectivity, which is roughly 3 folds higher than SnO2/SnS2 single Z-scheme heterojunction. By using in-situ diffuse reflectance infrared Fourier-transform spectroscopy, we observe that ethanol is produced through a *COCOH pathway, in which Cu2SnS3 would decrease the activation energy barrier from *COOH to *CO.

Visible-blind near-infrared organic photodetectors

The presently available commercial photodetectors have a broadband photoresponse and require different external optical filters to block the undesired light outside the detection spectrum window, e.g., near-infrared (NIR) detection. The use of an NIR bandpass has technical limitations in curved or flexible large-area photodetectors, as an NIR bandpass depends critically on the difference in the interference of the optical path in the filter. This work reports the effort to develop a high-performance filter-free organic photodetector (OPD) with a double bulk heterojunction (BHJ) structure. The visible-blind NIR photodetection is realized by eliminating the photocurrent generated in the front visible light-absorbing BHJ optical depletion layer, due to the suppression of electron transport by incorporating a copper thiocyanate-based electron-blocking layer in the OPD. Only excitons generated in the rear NIR-absorbing BHJ contribute to photocurrent in the OPD, thereby achieving visible-blind NIR photodetection. The double BHJ OPD has a high responsivity of 0.38 A/W at 1050 nm and a specific detectivity of >1013 Jones over the wavelength range from 800 to 1050 nm, making it an ideal candidate for applications in optical communication, food quality detection, wellness monitoring, and NIR image sensors.

Graphdiyne (g-CnH2n-2) nanosheets encapsulated Cu-Co Prussian blue Analogues formed double S-scheme heterojunction for wide spectrum photocatalytic H2 evolution

The frontier of sustainable energy research includes the advancement and creation of stable and efficient photocatalysts for the process of photocatalytic hydrogen evolution (PHE). Graphdiyne (GDY), an innovative carbon allotrope, demonstrates a narrow band gap and exceptional photogenerated charge mobility, making it extremely promising in the field of photocatalysis. In addition, Prussian Blue Analogues (PBA) are a unique category of metal–organic frameworks (MOFs) with open framework structures and strong stability. Compounds formed by ligands and various metal ions in PBA materials exhibit excellent performance. This work primarily enhances wide spectrum PHE by in situ growing GDY nanosheets onto Cu-Co PBA to construct a double S-scheme Cu-Co PBA@GDY/CuI (CCGC) heterojunction. The amorphous GDY can provide abundant active sites for photocatalytic hydrogen evolution reaction. Furthermore, the nanosheet properties of GDY were confirmed using Atomic Force Microscopy (AFM). The highest PHE rate of Cu-Co PBA@GDY/CuI-10 (CCGC-10) reaches 12947.8 μmol h−1 g−1 with a apparent quantum efficiency (AQE) of is 4.37 % at 520 nm, and exhibits good cycling stability. Based on the bandgap matching theory, the spatial behavior of photogenerated carriers in GDY, CuI, and Cu-Co PBA was effectively controlled, resulting in a close interface with a double S-scheme heterojunction charge transfer in Cu-Co PBA@GDY/CuI. The S-scheme photogenerated charge transfer pathway in CCGC was further confirmed through in-situ XPS, electron spin resonance (ESR) and work function (Wf). This work proposes a novel approach for the synthesis of solar energy conversion composite photocatalysts based on GDY and PBA.

Improving the efficiency of a CIGS solar cell to above 31% with Sb2S3 as a new BSF: a numerical simulation approach by SCAPS-1D.

The remarkable performance of copper indium gallium selenide (CIGS)-based double heterojunction (DH) photovoltaic cells is presented in this work. To increase all photovoltaic performance parameters, in this investigation, a novel solar cell structure (FTO/SnS2/CIGS/Sb2S3/Ni) is explored by utilizing the SCAPS-1D simulation software. Thicknesses of the buffer, absorber and back surface field (BSF) layers, acceptor density, defect density, capacitance-voltage (C-V), interface defect density, rates of generation and recombination, operating temperature, current density, and quantum efficiency have been investigated for the proposed solar devices with and without BSF. The presence of the BSF layer significantly influences the device's performance parameters including short-circuit current (Jsc), open-circuit voltage (Voc), fill factor (FF), and power conversion efficiency (PCE). After optimization, the simulation results of a conventional CIGS cell (FTO/SnS2/CIGS/Ni) have shown a PCE of 22.14% with Voc of 0.91 V, Jsc of 28.21 mA cm-2, and FF of 86.31. Conversely, the PCE is improved to 31.15% with Voc of 1.08 V, Jsc of 33.75 mA cm-2, and FF of 88.50 by introducing the Sb2S3 BSF in the structure of FTO/SnS2/CIGS/Sb2S3/Ni. These findings of the proposed CIGS-based double heterojunction (DH) solar cells offer an innovative method for realization of high-efficiency solar cells that are more promising than the previously reported traditional designs.

Novel CoV-LDH/GDY/CuI tandem double S-scheme heterojunction based on graphdiyne (g-CnH2n−2) toward photocatalytic hydrogen evolution

A ternary system of CoV-LDH/GDY/CuI double S-scheme heterojunction based on morphology modulation and energy band structure was successfully constructed, providing a new idea for the construction of a rational and efficient photocatalytic system.

A novel dual S-scheme Co9S8/MnCdS/Co3O4 heterojunction for photocatalytic hydrogen evolution under visible light irradiation.

Rational design and synthesis of a unique heterojunction photocatalyst structure is an important strategy to enhance its performance and structural stability. Herein, Co9S8/MnCdS/Co3O4 photocatalysts with double S-scheme heterojunctions were successfully prepared by coupling Co9S8 and Co3O4 sheet structures with n-type MnCdS nanoparticles through a simple solvothermal and mechanical mixing method. The construction of the dual S-scheme heterostructure offers the possibility to expand the light absorption range, extend the carrier lifetime and maximise the redox capacity. In addition, the mechanism of charge transfer and the reason for the improvement of photocatalytic activity were explored through photoelectrochemical characterization. The lamellar structures of Co9S8 and Co3O4 not only provide excellent dispersion and slow down the agglomeration of MnCdS nanoparticles, but also promote charge transfer, which improves the photocatalytic hydrogen production effect. Under simulated solar irradiation, the evolution rate of H2 after 5 h was as high as 46.44 μmol, which was 3.49 and 1.49 times higher than those of pristine MnCdS and MnCdS/Co3O4, respectively. Meanwhile, it has good stability under 20 h irradiation. This work demonstrates a novel idea for the rational design of double S-scheme photocatalysts with efficient space separation.

Electrosynthesized fluorinated polybithiophenes for ammonia sensing

The dependence of the nature of majority charge carriers on the fluorination degree of polymers in double lateral heterojunction devices.

Designing a Schottky coupled p–n junction to enhance the kinetic behavior of the oxygen evolution reaction

The design of the energy band structure modulates the surface charge distribution and optimizes energy levels of Fe3C-NG@NiFe, the construction of the double heterojunction introduces additional active sites and fast electron transfer for the OER.

Synthesis of double Z-scheme CdS/Bi2O2CO3/BiOCl heterojunction photocatalysts for degradation of rhodamine B under visible light

A novel double heterojunction structure provides rapid electron transfer paths, which can degrade rhodamine B efficiently.

Experimental Evaluation of Tailored Double Heterojunction Non-Toxic Metal Oxide-Based Nanostructured Sensor for Multi-Sensing Application

Experimental Evaluation of Tailored Double Heterojunction Non-Toxic Metal Oxide-Based Nanostructured Sensor for Multi-Sensing Application

High efficiency treatment of antibiotic wastewater by self-assembled coated double heterojunction TiO2/g-C3N4/BN photocatalyst

The treatment of antibiotic wastewater is one of the environmental problems that humans must solve. Low cost and high activity photocatalyst are the key to the treatment of antibiotic wastewater...

GeSe-embedded metal-oxide double heterojunctions for facilitating self-biased and efficient NIR photodetection.

Infrared radiation detection is significantly important in communication, imaging, and sensing fields. Here, we present the integration of germanium selenide (GeSe) with a metal-oxide heterojunction to achieve efficient near-infrared (850 nm) photodetection under zero bias conditions. Nickel oxide (NiO) and silicon (Si) formed a favorable energy band alignment for the efficient separation of photogenerated charge carriers, resulting in a high figure of merits. The additional incorporation of a germanium selenide (GeSe) interlayer between the nickel oxide (NiO) and silicon (Si) heterojunction improved the external responsivity (from 0.22 to 3300 mA W-1), detectivity (from 1.24 × 107 to 20 × 109 Jones), normalized photocurrent to dark current ratio (from 4 × 103 to 3 × 105 W-1), noise equivalent power (from nW to pW), and rise/fall time (from 34/34.5 ms to 14/13 ms). The interlayer introduction of a semiconductor in various heterojunctions can facilitate self-biased and broadband photodetection for widely used optoelectronic applications.

Reinforcement of Electrocatalytic Oxygen Evolution Activity Enabled by Constructing Silver-Incorporated NiCo-PBA@NiFe-LDH Hierarchical Nanoboxes.

Complicated oxygen evolution reaction (OER) poses the bottleneck in improving the efficiency of hydrogen production through water electrolysis. Herein, an integrated strategy to modulate the electronic structure of NiFe layered double hydroxide (NiFe-LDH) is reported by constructing Ag-incorporated NiCo-PBA@NiFe-LDH heterojunction with a hierarchical hollow structure. This "double heterojunction" facilitates local charge polarization at the interface, thereby promoting electron transfer and reducing the adsorption energy of intermediates, ultimately enhancing the intrinsic activity of the catalyst. It is noteworthy that an exchange bias field is observed between NiCo-PBA and NiFe-LDH, which will be conducive to regulating the electron spin states of metals and facilitating the production of triplet oxygen. Additionally, the unique hierarchical nanoboxes provide a large specific surface area that ensures adequate exposure to adsorption sites and active sites. Profiting from the synergistic advantages, the overpotential is as low as 190mV at a current density of 10mAcm-2, with a low Tafel slope of 21mVdec-1. Moreover, density functional theory (DFT) calculation further substantiated that the incorporation of Ag in the heterojunction can effectively reduce the adsorption energy of reactant intermediates and enhance the conductivity.

Bi3O4Cl/g-C3N4/Cd0.5Zn0.5S Double Z-Scheme Heterojunction Photocatalyst for Highly Selective CO2 Reduction to Methane.

Solar-energy-driven CO2 hydrogenation is a promising strategy to alleviate the climate crisis. Methane is a desirable derivative of CO2 reduction. However, developing a photocatalyst for highly active and selective CH4 generation remains challenging. Herein, we report a double Z-scheme Bi3O4Cl/g-C3N4/Cd0.5Zn0.5S photocatalyst for efficient reduction of CO2 to CH4. In situ characterization techniques confirmed that the charge migration mechanism in Bi3O4Cl/g-C3N4/Cd0.5Zn0.5S promotes charge separation through double internal electric fields. As a result, the optimized C0.01B0.02C catalyst displayed a formation rate high up to 25.34 μmol g-1 h-1 and a selectivity of 96.52% of CH4. Moreover, the AQY of CO2 conversion on C0.01B0.02C (1.84%) was almost 41 times higher than that of the bare CN. This study provides a novel perspective to develop heterojunction photocatalysts for selective CO2 conversion to CH4.

Investigation of In0.7Ga0.3As/Ga0.5As0.5Sb-Based Heterojunction TFET with Ferroelectric Gate Dielectric for Performance and Reliability

This paper investigates In[Formula: see text]Ga[Formula: see text]As/Ga[Formula: see text]As[Formula: see text]Sb-based Heterojunction Tunnel Field Effect Transistor with ferroelectric dielectric as stack layer, namely Ferroelectric Dual Material Stacked Double Gate Heterojunction TFET (FDMSDG-HJTFET) for the first time for performance and reliability. Ferroelectric gate dielectric has been inculcated in the device design in addition to the doping of Ga[Formula: see text]As[Formula: see text]Sb in the source region and In[Formula: see text]Ga[Formula: see text]As in the drain region, respectively. The performance of the proposed device is quantified in terms of DC electrical parameters and short channel parameters. The reliability analysis of the proposed device has been carried out in terms of influence of variations of interface trap charges, gate-source overlap length and temperature on the device transfer characteristics. From the simulation results, it can be manifested that the proposed device presents superior DC electrical characteristic and reduced short channel effects as compared to the GaSb/Si Dual Material Stacked Double Gate Heterojunction TFET (GaSb/Si DMSDG-HJTFET), under the influence of group III–V materials and ferroelectric gate dielectric. In addition to this, the proposed device depicts elevated immunity to presence of interface trap charges at the interface, variations in gate-source overlap length and temperature variations as well. The implication of TiO2 as dielectric stack over SiO2 provides exceptional capacitive coupling at the interface and thus assists in the improvement of electrical characteristics of the device by enhancing the electric field. The outcome of the simulation results presents that Ga[Formula: see text]As[Formula: see text]Sb/In[Formula: see text]Ga[Formula: see text]As-based Ferroelectric Dual Material Stacked Double Gate Heterojunction TFET (FDMSDG-HJTFET) can prove to be a competitive alternative for high performance applications with improved reliability. The design and simulation of the proposed device structure has been executed using technology computer-aided design (TCAD) tool.

NiTiO3/Bi2O3/MoS2 double Z-type heterojunction catalysts realize dual-function applications of photocatalytic fuel cells and lactic acid sensing

Sensors in intelligent monitoring and personal healthcare generally face power supply problems, such as cycle charging, regular maintenance, and battery replacement, which greatly limit the applications of sensing devices. Self-powered sensing system with a visible-light-driven photo-fuel cell (PFC) exhibits the advantage of not requiring any external power source for the chemical sensing of analytes. In this work, an enzyme-free PFC self-powered sensing platform was established for sensing sweat lactate using photoelectric conversion technology. A NiTiO3/Bi2O3/MoS2 double Z-type heterojunction system was prepared by electrostatic interaction and self-assembly as the anode of the PFC. NiTiO3, Bi2O3 and MoS2 formed a double Z-type heterojunction system accelerated the electron transfer and improved the light absorption and photocatalytic efficiency, which in turn improved the perception of LA. In addition. lactic acid sensing experiments showed that the prepared non-enzymatic photoelectrochemical sensors had good detection performance. The assay results showed that the prepared biosensor has a wide detection range (30 μM-5 mM), low detection limit (6 μM), high selectivity(8μA μM−1 cm−2) and long-term stability. These assay results demonstrate its potential for applications in fields such as biomedicine and drug analysis.