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Double fullerene cathode buffer layers afford highly efficient and stable inverted planar perovskite solar cells
摘要： Fullerene derivatives especially [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) with strong electron-accepting abilities have been commonly implemented as indispensable cathode buffer layers (CBLs) of inverted (p-i-n) planar perovskite solar cells (iPSCs) to facilitate electron transport. However, only a single fullerene CBL is typically used in iPSC devices, resulting in interfacial energy offset between fullerene CBL and metal cathode and consequently insufficient electron transport. Herein, we synthesized a novel bis-dimethylamino-functionalized fullerene derivative (abbreviated as PCBDMAM) and applied it as an auxiliary fullerene interlayer atop of PCBM to form a PCBM/PCBDMAM double fullerene CBL, leading to dramatic enhancement of both efficiency and ambient stability of iPSC devices. Incorporation of PCBDMAM interlayer facilitates the formation of interfacial dipole layer between PCBM and Ag cathode, resulting in decrease of the work function of the Ag cathode. As a result, the CH3NH3PbI3 (MAPbI3) iPSC devices based on PCBM/PCBDMAM double fullerene CBL exhibit the highest power conversion efficiency (PCE) of 18.11%, which is drastically higher than that of the control device based on single PCBM CBL (14.21%) and represents the highest value reported for double fullerene CBL-based iPSC devices. Moreover, due to the higher hydrophobicity of PCBDMAM than PCBM, iPSC devices based on PCBM/PCBDMAM double fullerene CBL shows an enhanced ambient stability, retaining 67% of the initial PCE after storage 1440 h exposure under the ambient atmosphere without any encapsulation, whereas only 43% retaining was achieved for the control device based on single PCBM CBL.
关键词： Cathode buffer layer,Perovskite solar cells,Work function,Interfacial engineering,Fullerene derivative
更新于2025-09-23 15:21:01
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Two stage modelling of solar photovoltaic cells based on Sb2S3 absorber with three distinct buffer combinations
摘要： Solar cell research has always been an attraction by virtue of its clean and green status. However, to overcome the implications of high cost and moderate efficiency, there has always been fierce competition to search alternative approach for designing efficient solar cells with optimal performance-cost ratio. Recently, antimony sulfide (Sb2S3) has received substantial attention as an absorber in thin film solar cells due to earth abundance, low cost, non-toxic property and high optical absorption. Still, its performance could not match Si based cells. In this work, we adopted two-stage simulation approach to design Sb2S3 absorber based heterojunction solar cell to enhance efficiency. Initial simulation for configuration optimization was done considering thickness, defect density, recombination (radiative, Auger) effect, carrier density of the Sb2S3 absorber layer. Buffer layer thickness and absorption coefficient optimization was taken up. Further, series and shunt resistance of the device as well as conduction band offset (CBO) at absorber/buffer interface was also optimized at initial stage only. In the next level of simulation, efficiency enhancement was achieved by optimizing optimal back contact metal work function, absorber layer band gap grading and temperature. The aforesaid two-stage optimization yielded efficiency ~24.81%, which is higher than conventional thin film solar cell. The optimal solar cell structure configuration, for Sb2S3 absorber solar cell, suggested a positive CBO of 0.26 eV (e.g.; ZnS buffer layer), a back contact metal work function of 5.1 eV (e.g.; Mo, Au) and band gap grading window ~1.31 to 1.62 eV.
关键词： Conduction band offset,Sb2S3 solar cell,Work function,Band gap grading,Simulation
更新于2025-09-23 15:21:01
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van der Waals epitaxial growth of single crystal α-MoO3 layers on layered materials growth templates
摘要： Monolayer and multilayer α-MoO3 nanosheets are successfully grown on a 2D substrate by simply evaporating amorphous molybdenum oxide thin film in ambient conditions. A single-crystal α-MoO3 nanosheet without grain boundary is epitaxially grown on various 2D substrates despite a large lattice mismatch. During growth, the quasi-stable monolayer α-MoO3 first covers the 2D substrate, then additional layers are continuously grown on the first monolayer α-MoO3. The band gap of the α-MoO3 increases from 2.9 to 3.2 eV as the thickness decreases. Furthermore, due to oxygen vacancies and surface adsorbates, the synthesized α-MoO3 is highly n-doped with a small work function. Therefore, α-MoO3 field-effect transistors (FETs) exhibit a typical n-type conductance. This work shows the great potential of ultra-thin α-MoO3 in 2D-material-based electronics.
关键词： work function,van der Waals epitaxy,band structure,vacancy,transition metal oxide,stability,2D materials,lattice mismatch,transistor,heterostructure
更新于2025-09-23 15:21:01
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Improved visible-light photocurrent based on ZnO/ZnS core–shell nanorods via interfacial engineering
摘要： Vertically aligned quasi two-dimensional (2D) ZnO nanorods (NRs) on carbon fiber paper were prepared by a modified hydrothermal approach, an individual ZnO nanorod has a diameter of 100–200 nm and a length of ~1 μm. ZnO/ZnS core-hell hierarchal structures with an outer ZnS shell of ~25 nm were fabricated under an elaborate sulfidation treatment. Compared to ZnO NRs a depressed near band emission at 380 nm and a significant enhanced visible light emission around 500 nm were observed for the ZnO/ZnS core-hell NRs from photoluminescence spectra. XPS and ESR measurements were carried out to study the ions constituents and the defects of the prepared samples. The prepared samples were used as photoelectrodes in visible-light self-powered photoelectrochemical cell-type detector. And an enhanced photocurrent of 6.79 μA was obtained, which is ten times as high as that of the bare ZnO electrode. The results show that the existence of sulfur vacancies and the formation of ZnO/ZnS heterostructure were able to promote photocurrent performance, the former increases the carrier concentration and leads to an upshift of work function; the latter makes the band bend and the photogenerated e–p pairs can be separated efficiently. The results will be helpful to implement visible-light device based on heterostructure via interfacial engineering.
关键词： visible light,carbon paper,work function,photoelectrochemical cell-type detector,ZnO/ZnS core–shell
更新于2025-09-23 15:21:01
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Work Function-Tunable Graphene-Polymer Composite Electrodes for Organic Light-Emitting Diodes
摘要： Graphene has been regarded as one of the most promising transparent electrodes in flexible optoelectronic devices. Tremendous efforts have been paid on tuning the work function of graphene, which make significant contributions to improve the device performance. In this work, we propose to modify single layer graphene film with ultrathin high dielectric polymers, including polyvinylidene chloride (PVDC) and polyvinylidene difluoride (PVDF) with the dielectric constants of 4.7 and 8.4, respectively. Ultraviolet photoelectron spectroscopy confirms the formation of interfacial dipoles induced by the high dielectric polymers, and the work function can be tuned from 4.6 eV for pristine graphene to 4.72 and 4.94 eV for PVDF and PVDC modified graphene, respectively. Accordingly, organic light-emitting diodes (OLEDs) are fabricated, and the one based on PVDC-modified graphene composite electrode obtained the highest current efficiency of 80.0 cd/A with a 1.27-fold enhancement compared with the pristine counterpart. This work provides an alternative strategy of interfacial dipole to surface chemical doping method to tune the work function of graphene electrodes, and the utilization of a polymer with high dielectric constant to modify graphene successfully realized the fabrication of highly efficient OLEDs.
关键词： graphene,work function,high dielectric polymer,interface dipole,OLEDs
更新于2025-09-23 15:19:57
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Interfacial Band Engineering of MoS <sub/>2</sub> /Gold Interfaces Using Pyrimidine-Containing Self-Assembled Monolayers: Toward Contact-Resistance-Free Bottom-Contacts
摘要： Bottom-contact architectures with common electrode materials such as gold are crucial for the integration of 2D semiconductors into existing device concepts. The high contact resistance to gold—especially for bottom contacts—is, however, a general problem in 2D semiconductor thin-film transistors. Pyrimidine-containing self-assembled monolayers on gold electrodes are investigated for tuning the electrode work functions in order to minimize that contact resistance. Their frequently ignored asymmetric and bias-dependent nature is recorded by Kelvin probe force microscopy through a direct mapping of the potential drop across the channel during device operation. A reduction of the contact resistances exceeding two orders of magnitude is achieved via a suitable self-assembled monolayer, which vastly improves the overall device performance.
关键词： work-function engineering,MoS2,thin-film transistors,self-assembled monolayers,Schottky barrier
更新于2025-09-23 15:19:57
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Numerical simulation for optimization of an ultra-thin n-type WS2/p-type c-Si heterojunction solar cells
摘要： Recently, ultra-thin tungsten disul?de (WS2) has become one of the hot spots in the research of solar cell materials due to its excellent optical and electrical properties. In this study, we use AFORS-HET software version 2.5 at air mass 1.5 to simulate the structure of n-type WS2/p-type c-Si heterojunction solar cells. Our goal is to ?nd an appropriate way to improve the performance of n-type WS2/p-type c-Si heterojunction solar cells by simulation. Through optimizing the parameters of both WS2 layer and Si layer, we obtain a maximum photovoltaic conversion e?ciency of 20.57%. Subsequently, we investigate the in?uence of the ITO work function and the interface states on the performance of n-type WS2/p-type c-Si heterojunction solar cells. It’s found that through selecting the suitable ITO work function and decreasing the interface defect density, solar cell’s performance can be further improved. Our result indicates that ultra-thin WS2 is a promising photovoltaic material for the application in solar cells.
关键词： Work function,Heterojunction solar cells,Numerical simulation,Tungsten disul?de,Interface states
更新于2025-09-23 15:19:57
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Optoelectronic Properties of Electron Beam-Deposited NiOx Thin Films for Solar Cell Application
摘要： The fabrication of highly efficient nickel oxide (NiOx) thin film for optoelectronic devices is a challenging task because optoelectronic properties are considerably influenced by deposition technique and film thickness. The effect of thickness on the film properties of electron beam–physical vapour-deposited NiOx thin film has been investigated in this work. The influence of post-annealing treatment on the optoelectronic properties of the film was compared with that of the as-deposited one. Optical transparency gradually decreased upon the successive increment in thickness of the as-deposited and annealed films. The surface roughness of as-deposited films increased linearly with the increase in film thickness, but this behaviour was altered in post-annealed films. Spherical grains with high packing density were observed on the as-deposited films, but the grain size was altered substantially on the post-annealed films. The annealed films presented a higher work function than their corresponding as-deposited films. This work presents important insights into the design of photovoltaic devices with an effective deposition process, including a high material utilisation.
关键词： thickness,work function,NiOx,electron beam vapour deposition,annealing,opto-electronic
更新于2025-09-23 15:19:57
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[IEEE 2019 URSI Asia-Pacific Radio Science Conference (AP-RASC) - New Delhi, India (2019.3.9-2019.3.15)] 2019 URSI Asia-Pacific Radio Science Conference (AP-RASC) - Generation of Pulsed Fiber Laser: ns to fs domain
摘要： Thermionic energy converter (TEC) is a heat engine that generates electricity directly using heat as its source of energy and electron as its working fluid. Despite having a huge potential as an efficient direct energy conversion device, the progress in vacuum-based thermionic energy converter development has always been hindered by the space charge problem and the unavailability of materials with low work function. It is only recently that researchers have started to look back into this technology as recent advances in manufacturing technology techniques have made it possible to solve these problems, making TECs a viable option in replacing current energy production systems. The focus of this paper is to review the challenges of producing efficient and practical TECs, along with recent findings and developments in mitigating these challenges. Furthermore, this paper looked into potential applications of TECs, based on recent works and technologies, and found that, with certain improvements, it can be applied in many sectors.
关键词： nanowires,work function,thermionic energy conversion (TEC),space charge,Energy conversion efficiency
更新于2025-09-23 15:19:57
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Tunable Work Function of MgxZn1-xO as a Viable Friction Material for Triboelectric Nanogenerator
摘要： Since the invention of triboelectric nanogenerators (TENGs), their output performance has been improved through various approaches such as material surface modification, device structure optimization and so on, but rarely through the development of new friction materials. In this work, magnetron sputtered MgxZn1-xO film is developed as a viable friction material, that rubs against polydimethylsiloxane (PDMS) in TENG. The work function, measured by Kelvin probe microscopy, of the MgxZn1-xO films can be effectively tuned by varying Mg composition, x, and exposed surface facets, which are shown to dominate the charge transfer behavior. In addition, film thickness also plays an important role, affecting the output performance. The output voltage and total charge of a TENG with MgxZn1-xO film are demonstrated to be tremendously enhanced by 55 and 90 times, respectively, compared to that of a TENG with ZnO film. Even more intriguingly, the tribo-output polarity can be reversed by adjusting the relative work function through varying the preferred growth orientation of the MgxZn1-xO film, for a given value of Mg content.
关键词： surface facet,triboelectric nanogenerator,work function,ZnO,MgxZn1-xO,thickness effect
更新于2025-09-23 15:19:57