Inorganic Heterojunction Research Articles

An Organic−Inorganic Heterojunction Electrocatalyst for Highly Efficient Urea Oxidation

Constructing p−n heterojunction allows the modulation of the interface electronic structure and boosts electron transfer, leading to enhanced electrocatalytic performance. Herein, an organic−inorganic heterojunction electrocatalyst made of Ni(OH)2, triazine−based covalent...

Bio‐Inspired Artificial Retinas Based on a Fibrous Inorganic–Organic Heterostructure for Neuromorphic Vision

AbstractTo create artificial visual perception systems, artificial retina structures that can imitate the behavior of the biological retina in human vision are of great interest. However, these devices have limited abilities to emulate the structure and working principles of human retinas and the fiber‐shaped structure of optic nerves. Here, a bio‐inspired artificial retina based on a fibrous photonic artificial synapse (FPAS) formed by organic–inorganic heterojunctions on a single fiber is proposed. The two‐terminal structure of the FPAS can emulate the structure and working principle of the human retina, fiber‐shaped optic nerves, and the synaptic functions of optic neurons. The proposed FPAS is operated without external power by modulating the capture and release of photo‐generated carriers and the photo‐gating effect at the barriers formed by organic–inorganic heterojunctions. A bio‐inspired artificial retina structure can be created by aligning an FPAS on a flexible substrate to detect and memorize patterned ultraviolet light distribution for a certain period of time, after which the stored pattern image gradually decays. This artificial bio‐inspired retina device has great potential for use in wearable fiber‐structured neuromorphic visual systems.

Zero‐Dimensional Tin Halide Perovskite with Long Charge Carrier Lifetime and Anisotropic Photoconductivity for Selective Deep‐UV Photodetection

AbstractThe rapid evolution of research on efficient and cost‐effective materials for UV photodetection is driven by their applications in environmental monitoring, medical diagnosis, security systems, and scientific research. In this study, a novel zero‐dimensional tin (IV) halide perovskite, (AEHB)2SnBr6, is synthesized for UV‐photodetector application. The material shows anisotropic photoconductivity with conductivity values of 8.4 × 10−5 and 4.0 × 10−5 cm2 V−1 s−1 in the parallel and perpendicular directions to the long crystal axis, respectively. Its film state demonstrated photoconductivity approximately three times higher than that of its crystalline state. The material has a substantial charge carrier lifetime of 37 µs in the crystalline form and 57 µs in the film state, which can be attributed to its quantum‐well‐like structure and type‐IIb band alignment at the organic–inorganic heterojunction, as evident from single‐crystal X‐ray diffraction analysis and density functional theory calculations. A UV photodetector is fabricated with this material, demonstrating impressive device parameters, such as a high responsivity of 9.96 A W−1, a specific detectivity of 6.8 × 1011 Jones, and an external quantum efficiency of 49%. The device also showed a consistent photocurrent, fast photoresponse, and long‐term stability, making it a promising material for practical applications.

Parallel Planar Heterojunction Strategy Enables Sb2S3 Solar Cells with Efficiency Exceeding 8 %

AbstractSolution‐processed solar cells based on inorganic heterojunctions provide a potential approach to the efficient, stable and low‐cost solar cells required for the terrestrial generation of photovoltaic energy. Antimony trisulfide (Sb2S3) is a promising photovoltaic absorber. Here, an easily solution‐processed parallel planar heterojunction (PPHJ) strategy and related principle are developed to prepare efficient multiple planar heterojunction (PHJ) solar cells, and the PPHJ strategy boosts the efficiency of solution‐processed Sb2S3 solar cells up to 8.32 % that is the highest amongst Sb2S3 devices. The Sb2S3‐based PPHJ device consists of two kinds of conventional planar heterojunction (PHJ) subcells in a parallel connection: Sb2S3‐based PHJ subcells dominating the absorption and charge generation and CH3NH3PbI3‐based PHJ subcells governing the electron transport towards collection electrode, but it belongs to an Sb2S3 device in nature. The resulting PPHJ device combines together the distinctive structural features of Sb2S3 absorbing layer as a main absorber and the duplexity of well‐crystallized/oriented CH3NH3PbI3 layer in charge transportation as an additional absorber, while the presence of perovskite does not affect device stability. The PPHJ strategy maintains the facile preparation by the conventional sequential depositions of multiple layers, but eliminates the normal complexity in both tandem and parallel tandem PHJ systems.

Parallel Planar Heterojunction Strategy Enables Sb2 S3 Solar Cells with Efficiency Exceeding 8 .

Solution-processed solar cells based on inorganic heterojunctions provide a potential approach to the efficient, stable and low-cost solar cells required for the terrestrial generation of photovoltaic energy. Antimony trisulfide (Sb2 S3 ) is a promising photovoltaic absorber. Here, an easily solution-processed parallel planar heterojunction (PPHJ) strategy and related principle are developed to prepare efficient multiple planar heterojunction (PHJ) solar cells, and the PPHJ strategy boosts the efficiency of solution-processed Sb2 S3 solar cells up to 8.32 % that is the highest amongst Sb2 S3 devices. The Sb2 S3 -based PPHJ device consists of two kinds of conventional planar heterojunction (PHJ) subcells in a parallel connection: Sb2 S3 -based PHJ subcells dominating the absorption and charge generation and CH3 NH3 PbI3 -based PHJ subcells governing the electron transport towards collection electrode, but it belongs to an Sb2 S3 device in nature. The resulting PPHJ device combines together the distinctive structural features of Sb2 S3 absorbing layer as a main absorber and the duplexity of well-crystallized/oriented CH3 NH3 PbI3 layer in charge transportation as an additional absorber, while the presence of perovskite does not affect device stability. The PPHJ strategy maintains the facile preparation by the conventional sequential depositions of multiple layers, but eliminates the normal complexity in both tandem and parallel tandem PHJ systems.

G-C3N4/PDI@ZnIn2S4 2D/2D organic–inorganic hybrid heterojunction with enhanced visible light photocatalytic property

In this study, we designed and fabricated novel g-C3N4/PDI@ZnIn2S4 2D/2D organic/inorganic hybrid heterojunctions consist of g-C3N4/PDI nanosheets and ZnIn2S4 nanosheets by a two-step-heating route followed by an oil-bath process for the first time. The synthesized heterojunctions were used as photocatalysts for the visible-light photodegradation of Rhodamine B (RhB), the composite photocatalysts displayed enhanced photocatalytic performance. Among them, the optimal photocatalyst exhibited significantly enhanced photocatalytic activity of up to 83.92 % after 120 min, which is nearly 7.0, 2.2, and 1.4 times higher than that of bare g-C3N4, g-C3N4/PDI, and ZnIn2S4, respectively. The enhanced photocatalytic activities can be attributed to the close interface contact and matched band structure between g-C3N4/PDI and ZnIn2S4, resulting in the formation of efficient heterojunctions, which accelerate the separation and transfer of photo-induced charges and improve the utilization of visible light. This work confirms the promising application prospects of g-C3N4/PDI@ZnIn2S4 photocatalysts in environmentalremediationfields.

Organic-inorganic photocatalyst with S-scheme heterojunction based proton shuttle strategy for efficient dye degradation

The organic–inorganic S-scheme heterojunction with proton shuttling ability has been proposed to enhance the treatment of organic dyes. A PS-PANI@ZnO photocatalyst combining cellulose, phytic acid and polyaniline was prepared to address the issues of difficult excitation and fast recombination of photogenerated electrons and carriers in common inorganic semiconductor photocatalysts. PS-PANI(100)@ZnO could achieve a high degradation rate (> 99%) of MO and RhB in 160 and 140 min, respectively. Moreover, the catalytic activity remained high under alkaline conditions, and the degradation rates could be maintained above 98% after five cycles. The specific surface area of ZnO was increased from 107.79 m2/g to 112.54 m2/g after modification, in which phytic acid could provide more active sites for the reduction of O2 to •O2−. In addition, the PS-PANI can effectively reduce the band gap of ZnO. PS-PANI(50,100,150,200)@ZnO were 3.148, 3.133, 3.068, and 3.100 eV, respectively. The economic cost analysis of the prepared catalysts showed that the cost was approximately 37% higher while the degradation effect was enhanced by 4 times. Meanwhile, environmental toxicity tests showed that the treated wastewater had low toxicity for mung bean seed growth.

In situ topotactic formation of the pn-type inorganic intergrowth bulk heterojunction NiO(Al)/CuO(Ni,Al) for photocatalytic CO2 methanation

Considering that photosynthetic CH4 seems to have a high energy density, it serves as a powerful way for storing renewable energy. In this work, a potential pn-type inorganic intergrowth bulk heterojunction (pn-IIBH) NiO(Al)/CuO(Ni,Al) was designed and obtained by the precursor CuNiAl-layered double hydroxides with two-stage topological pyrolysis (TTP) method. The microstructure was investigated in detail EXAFS to understand in-situ topotactic formation of the IIBH. Then, by using ISI-XPS, and fs-TAS, the transfer mechanism of the photogenerated electrons in NiO(Al)/CuO(Ni,Al) was explored which met pn-type heterojunction. Furthermore, it was screened for CO2 photoreduction to target CH4 (86.59 μmol/g·h) and O2 (150.84 μmol/g·h) from H2O and the selectivity of CH4 reached more than 87.13%. Finally, in-situ IR and DFT calculation demonstrated that CO2 methanation by the hydrogenation pathway occurred and the Ni doping in the pn-IIBH activated CO2 adsorption more effectively. This work offers an approach to photocatalysis development in CO2 methanation.

Synergistic effect of Z-scheme junction and core–shell architecture over NH2-MIL-125@Ag@AgCl ternary heterojunction for cooperative CO and H2O2 production

Herein, a NH2-MIL-125(Ti)@Ag@AgCl (NM@Ag@AgCl) stacked core–shell heterojunction with Z-scheme carrier transfer mechanism was developed to fulfil the goal of synchronous reactions of CO2 reduction and H2O oxidation. In detail, the NM@Ag@AgCl was obtained by in-situ loading the AgCl as the shell-inorganic semiconductor on the octahedral NM as the core-organic semiconductor, followed by in-situ transforming part of the AgCl shell into the plasmonic Ag nanoparticles using a photo-reduction method. As a result, the interface effects of core–shell architecture majorized by the Ag electronic mediator can favor the transmission of photogenerated carriers and reduce electron transport resistance; while the plasmonic Ag mediated Z-scheme mode with a giant internal electronic field provided a strong driving force to recombine the carriers with weak redox ability, reserving the carrier with strong redox ability on the NH2-MIL-125-core and AgCl-shell for the simultaneous reactions. The CO and H2O2 yields of the optimal NM@Ag@AgCl were 6.02 and 5.43 μmol⋅g−1⋅h−1, which were 3.31 and 4.02 times that of the NM, respectively. This study furnishes a novel thread for the design of core–shell organic–inorganic heterojunction with high interfacial charge transfer for realizing the simultaneous reactions.

Establishment of a photoactive heterojunction of triazine covalent-organic polymer and copper (II) selenide: Photoelectrochemical aptasensing strategy for efficiently detecting Salmonella typhimurium

The sensitive determination of foodborne pathogens in foodstuffs or water system is essential for protecting food and environment safety. Herein, we have proposed a photoelectrochemical (PEC) aptasensor based on two-dimensional (2D)/3D organic–inorganic heterojunction for the efficient detection of Salmonella typhimurium (S. typhimurium). The heterojunction was established via the in situ growth of copper (II) selenide (CuSe) nanosheets around the photoactive triazine covalent-organic polymer (COP) nanospheres, which was synthesized using 2,4,6-Tris(4-aminophenyl)-1,3,5-Triazine (TAPT) and 2,4,6-trihydroxy-1,3,5-benzenetricarbaldehyde (Tp) as building blocks (denoted as TAPT-Tp-COP@CuSe). Integrating the features of TAPT-Tp-COP (such as large specific surface and pore size, multi-functionality, and rich defects) and CuSe (such as high photoabsorption ability, fast electron transfer and effective separation of the photo-generated charge carrier) not only can accelerate the photoelectric transformation efficiency, but also can promote the aptamer immobilization. Consequently, the constructed PEC aptasensor based on TAPT-Tp-COP@CuSe illustrated a low detection limit of 3.4 CFU mL−1 with a linear range from 1 × 101 to 1 × 105 CFU mL−1 toward S. typhimurium. In addition, it demonstrated high selectivity in light of the specific recognition of aptamer toward S. typhimurium, good reproducibility and stability, and promising regeneration ability, as well as wide applications for the detection of S. typhimurium in diverse foodstuffs systems. The present work provides a new aptasensing strategy for the effective detection of foodborne pathogens from diverse foodstuffs by combining the merits of COPs and PEC technique.

Enhanced Emission of Molybdenum Disulfide by Organic–Inorganic Hybrid Heterojunctions

Enhanced Emission of Molybdenum Disulfide by Organic–Inorganic Hybrid Heterojunctions

Mimicking evasive behavior in wavelength‐dependent reconfigurable phototransistors with ultralow power consumption

AbstractRetinal‐inspired synaptic phototransistors, which integrate light signal detection, preprocessing, and memory functions, show promising applications in artificial vision sensors. In recent years, it has been reported to construct heterojunction in phototransistors to realize positive photoconductance (PPC) and negative photoconductance (NPC) modulations, thereby achieving visible and infrared wavelength discrimination and various visual functions. However, relatively little attention has been paid to wavelength‐dependent switching and reconfigurability between two states (PPC and NPC), limiting further applications for complex simulations of biological visual functions. Here, a mixed organic–inorganic heterojunction synaptic phototransistor was constructed by integrating CsPbBr3 nanoplates (NPLs) with strong blue‐light absorption and poly(3‐hexylthiophene‐2,5‐diyl) (P3HT) with strong red‐light absorption. Compared with the three‐dimensional (3D) structure CsPbBr3 nanocubes (NCs), the two‐dimensional (2D) CsPbBr3 NPLs exhibited more efficient charge transfer with P3HT. Based on the individual optical absorption properties in organic–inorganic heterojunction, the device exhibited wavelength‐selective and reconfigurable behavior between PPC and NPC. A low power consumption of 0.053 fJ per synaptic event was achieved, which is comparable to a biological synapse. Finally, Drosophila's evasive behavior to food under red and blue light can be successfully demonstrated. This work demonstrates the future potential of synaptic phototransistors for visuomorphic computing.

Weak Light‐Stimulated Synaptic Transistors Based on MoS2/Organic Semiconductor Heterojunction for Neuromorphic Computing

Photonic synapses are expected to play an important role in implementing brain‐like computing owing to the wide bandwidth and low mutual interference of optical signals. Herein, photonic synaptic transistors based on inorganic semiconductor molybdenum disulfide (MoS2) and organic semiconductor heterojunction with adjustable short‐term/long‐term plasticity are proposed. Benefitting from the outstanding photosensitive characteristics originating from the heterojunction, the devices have the capability of weak light detection and can exhibit distinct synaptic responses even under an ultraweak light intensity of 40 nW cm−2, which is considerably lower than that of most previously reported photonic synaptic transistors. Furthermore, a low energy consumption of 0.4 fJ per synaptic event can be obtained at a low operating voltage of 0.001 V, lower than that required for a single synaptic event observed in human brains. In addition, the devices can implement high‐pass filtering function and illustrate the potential in image sharpening processing. More significantly, logic functions as well as associative learning behavior are dramatically simulated through all‐optical stimulation. This work demonstrates a feasible approach to developing multifunctional photonic synaptic transistors based on inorganic/organic semiconductor heterojunction for neuromorphic computing.

Space-Charging Interfacial Layer by Illumination for Efficient Sb2S3 Bulk-Heterojunction Solar Cells with High Open-Circuit Voltage

Solution-processed material systems for effective photovoltaic conversion are the key to low-cost and efficient solar cells. While antimony trisulfide (Sb2S3) is a promising photovoltaic absorber, solution-processed quality Sb2S3-based heterojunction systems for solar cells, particularly with an open-circuit voltage (Voc) higher than 0.70 V, are challenging issues. Here, a cadmium sulfide (CdS) interfacial engineering method is developed for the Sb2S3-based bulk-heterojunction (BHJ) solar cells with an efficiency of 6.14% and a Voc up to 0.76 V that is the highest one among solution-processed Sb2S3 solar cells. The prepared Sb2S3-based BHJ solar cells feature a Sb2S3 nanoparticle film interdigitated by a titania (TiO2) nanorod array with a nanostructured CdS shell as an interfacial layer on each TiO2 nanorod core. Upon understanding the interfacial interactions and band alignments in the TiO2-CdS-Sb2S3 system, the function of the CdS interfacial layer as a band-bended spatial spacer interacting strongly with both the TiO2 electron transporter and Sb2S3 absorber for increasing charge collecting efficiency is revealed; moreover, space-charging the band-bended CdS layer by illumination is found and a photogenerated interfacial dipole electric field model is proposed for understanding the high Voc subjected to the presence of the CdS interfacial layer. This work provides a conceptual guide for designing efficient inorganic heterojunction solar cells.

Carbon-based heterostructure from multi-photo-active nanobuilding blocks SrTiO3@NiFe2O4@Fe0@Ni0@CNTs with derived nanoreaction metallic clusters for enhanced solar light-driven photodegradation of harmful antibiotics

We reported on the sequential development of a high-operative photocatalyst with penta-component inorganic bulk heterojunction for improved charge trapping characteristics at particle–particle interfaces for enhanced solar light-driven photocatalytic degradation of active tetracycline antibiotic. Structural, morphological, optical, and electronic properties of the synthesized samples were investigated using a series of complementary characterization techniques, such as XRD, FE-SEM, HR-TEM, XPS, as well as hard and soft XAS in both total electron yield (TEY) and fluorescence yield (TFY). For the case of the carbon composite material, SrTiO3@NiFe2O4@Fe0@Ni0@CNTs, a reduced crystallinity when compared to the starting support material was noticed, although this translated into a significant improvement of the morphology and the photocatalytic performance. The SrTiO3@NiFe2O4@Fe0@Ni0@CNTs fibrous photocatalyst can efficiently achieve a high-to-total degradation of tetracycline antibiotic under visible light irradiation in less than two hours, following a non-linear PFO kinetic model with an apparent reaction rate of about 0.0606 min−1 and an 98% photodegradation activity. The XPS and XAS analysis demonstrated unequivocally the appearance of nanoscale zero-valent iron (Fe0) and zero-valent nickel (Ni0) on the photocatalyst surface, which facilitates the separation of photogenerated e+ and h+ pairs, and the appearance of more active sites.

SnS2-covalent organic framework Z-scheme van der Waals heterojunction for enhanced photocatalytic reduction of uranium (VI) in rare earth tailings wastewater

Uranium removal by photocatalytic reduction is one of the most promising methods to reduce radioactive contamination in wastewater. Herein, a Z-scheme van der Waals heterojunction photocatalyst (SnS2COF) was synthesized in situ by combining covalent organic frameworks (COF) with semiconductor (SnS2) for U (VI) reduction in rare earth tailings wastewater. The synthesis method of van der Waals heterojunction is simple and solves the problem of no hanging bond in composite components. In this heterojunction, large areas of van der Waals interaction form high-speed electron transport channels. In addition, it is deduced that SnS2COF fits the Z-scheme heterojunction electron transport mode through the theoretical calculation of the ground state and excited state electron density difference and the related band structure. Under the photoexcitation, the direction of electron flow is reversed, which further promotes the separation of the photogenerated electron (e−)-hole (h+) under the action of the built-in electric field, maintains the high reducibility of the conduction band, and avoids the photocorrosion of SnS2. Compared with inorganic-inorganic heterojunction, SnS2COF has a wider light absorption range, more active sites, and higher e−-h+ separation and transfer efficiency. Therefore, it had a higher U (VI) reduction removal capacity, up to 1123.3 mg g−1, far surpassing the SnS2 and COF counterparts under ultraviolet/visible light. And the U (VI) removal rate reached 98.5 % in rare earth tailings wastewater. The design concept of organic–inorganic heterojunction materials provides an alternative strategy for improving the photocatalytic performance.

The construction of a MAPbBr3/La2Ti2O7 organic–inorganic dual perovskite heterojunction for photocatalytic CO2 reduction

The MAPbBr3/La2Ti2O7 dual perovskite heterojunction with similar crystal structures, improved visible light absorption capacity and separation efficiency of charge carriers, thus exhibited enhanced photocatalytic CO2 reduction activity.

Air-stable ambipolar charge transport behaviors of organic-inorganic hybrid bilayer and application to Au nanoparticle-based floating gate memory

Ambipolar-based devices are considered effective alternatives in various applications, including reconfigurable logic, light-emitting transistors, and neuromorphic devices. On the other hand, the previously reported intrinsic single-layer ambipolar materials have limitations, such as high instability in ambient air and asymmetric transport of electrons and holes. In the present study, high air-stable and symmetrical ambipolar behavior were implemented using an organic-inorganic bilayer. An ambipolar-based memory application was implemented using these characteristics. This fabricated memory device used electrons and holes together with dinaphtho[2,3-b:2′,3′-f]thieno[3,2-b]thiophene organic p-type and zinc tin oxide inorganic n-type semiconductor heterojunction layers, resulting in wide memory window and high retention. In addition, these behaviors were analyzed at the band diagram level through ultraviolet photoelectron spectroscopy and ultraviolet-visible light spectroscopy, and chemical bonding was analyzed using x-ray photoelectron spectroscopy. These reports can provide useful strategies for applying various ambipolar applications in the future.

Sensitive photoelectrochemical sensor for detection of cancer biomarker based on enzyme embedded nanoparticles as signal probe

Photoelectrochemical (PEC) sensor was prepared for detection of cancer biomarker carcinoembryonic antigen (CEA), which is strongly associated with diagnosis and prognosis of different cancer. Organic semiconductor Y6 combined with gold nanoparticles (Au NPs) formed organic–inorganic heterojunction and the heterojunction was utilized as photoactive material. ZnPO4 nanoparticles with horseradish peroxidase (HRP) embedded inside the nanoparticle and antibody absorbed on nanoparticle surface were synthesized and utilized as signal probe. After formation of sandwich structure on electrode surface, HRP can catalyze 3,3′-dimethoxybenzidine (DB) in solution to form insulating polymer film, poly(3,3′-dimethoxybenzidine) (PDB) onto the electrode surface. The formed PDB film on electrode surface resulted in the suppression of PEC current intensity, achieving sensitive and selective detection of CEA with linear range from 1 pg/mL to 1 ng/mL and limit of detection of 0.5 pg/mL.

Research Progress on Graphitic Carbon Nitride/Metal Oxide Composites: Synthesis and Photocatalytic Applications.

Although graphitic carbon nitride (g-C3N4) has been reported for several decades, it is still an active material at the present time owing to its amazing properties exhibited in many applications, including photocatalysis. With the rapid development of characterization techniques, in-depth exploration has been conducted to reveal and utilize the natural properties of g-C3N4 through modifications. Among these, the assembly of g-C3N4 with metal oxides is an effective strategy which can not only improve electron-hole separation efficiency by forming a polymer-inorganic heterojunction, but also compensate for the redox capabilities of g-C3N4 owing to the varied oxidation states of metal ions, enhancing its photocatalytic performance. Herein, we summarized the research progress on the synthesis of g-C3N4 and its coupling with single- or multiple-metal oxides, and its photocatalytic applications in energy production and environmental protection, including the splitting of water to hydrogen, the reduction of CO2 to valuable fuels, the degradation of organic pollutants and the disinfection of bacteria. At the end, challenges and prospects in the synthesis and photocatalytic application of g-C3N4-based composites are proposed and an outlook is given.