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Oxidized Metal Schottky Contacts on (010) β-Ga2 O 3
摘要： Oxidized Ir, Pd, Pt, Ag, and Au Schottky contacts (SCs) were fabricated on (010) β-Ga2O3 single crystal substrates via reactive rf sputtering using an O2:Ar plasma. The use of in-situ oxidizing conditions resulted in SCs with very high rectifying barriers in excess of 2.0 eV for all the metals investigated, representing an increase of 0.4 to 0.9 eV compared to the corresponding plain metal versions. Both the plain and oxidized metal SCs showed evidence of Fermi Level pinning with their laterally homogeneous barrier heights lying in narrow ranges of ~1.3 to 1.5 eV and ~2.2 to 2.4 eV, respectively, with little correlation with metal work function. This was attributed to the influence of metal-induced oxygen vacancies and gap states at the SC interface, respectively. The very high barriers of the oxidized SCs resulted in excellent high temperature performance with ~10 orders of magnitude of rectification at 180 oC, indicating the potential of this technique for the fabrication of high temperature unipolar devices.
关键词： Metal Induced Gap States,Fermi Level Pinning,Oxygen Vacancies,Semiconductor Interfaces,Schottky Diodes
更新于2025-09-23 15:22:29
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An Electrical Analysis of a Metal-Interlayer-Semiconductor Structure on High-Quality Si <sub/> 1? <i>x</i> </sub> Ge <sub/><i>x</i> </sub> Films for Non-Alloyed Ohmic Contact
摘要： In this paper, we have investigated the effect of a metal-interlayer-semiconductor (MIS) structure on intrinsic silicon-germanium (SiGe) film which is epitaxially grown by ultra-high vacuum chemical vapor deposition (UHV-CVD). Ultra-thin dielectric materials can alleviate Fermi-level pinning at the metal/Si1?xGex contact region by preventing penetration into the Si1?xGex of metal-induced gap states (MIGS) from the metal surface. The electrical properties which are the back-to-back current density and specific contact resistivity of the Ti/TiO2/Si1?xGex structure improve at the TiO2 interlayer thickness of 0.5 nm for all kinds of Si1?xGex film with various levels of germanium (Ge) concentration. The case of Si0.7Ge0.3 film, the specific contact resistivity of a Ti/TiO2(0.5 nm)/Si0.7Ge0.3 structure is reduced 80-fold compared to that of a Ti/Si0.7Ge0.3 structure. The effect of the MIS structure has been well demonstrated on Si1?xGex film, and as a result this structure is suggested as a novel source/drain (S/D) contact scheme for advanced Si1?xGex complementary metal-oxide-semiconductor (CMOS) technology.
关键词： Epitaxial Growth,Metal-Interlayer-Semiconductor,Source/Drain Contact,Silicon-Germanium,Fermi-Level Pinning,Specific Contact Resistivity
更新于2025-09-23 15:22:29
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Omni-direction PERC solar cells harnessing periodic locally focused light incident through patterned PDMS encapsulation
摘要： Photovoltaic panels based on crystalline Si solar cells are the most widely utilized renewable source of electricity, and there has been a significant effort to produce panels with a higher energy conversion efficiency. Typically, these developments have focused on cell-level device modifications to restrict the recombination of photo-generated charge carriers, and concepts such as back surface field, passivated emitter and rear contact (PERC), interdigitated back contact, and heterojunction with intrinsic thin layer solar cells have been established. Here, we propose quasi-Fermi level control using periodic local focusing of incident light by encapsulation with polydimethylsiloxane to improve the performance of solar cells at the module-level; such improvements can complement cell-level enhancements. Locally focused incident light is used to modify the internal quasi-Fermi level of PERC solar cells owing to the localized photon distribution within the cell. Control of the local focusing conditions induces different quasi-Fermi levels, and therefore results in different efficiency changes. For example, central focusing between fingers enhances the current density with a reduced fill factor, whereas multiple local focusing enhances the fill factor rather than the current density. Here, these effects were explored for various angles of incidence, and the total electrical energy production was increased by 3.6% in comparison to a bare cell. This increase is significant as conventional ethylene vinyl acetate-based encapsulation reduces the efficiency as short-wavelength light is attenuated. However, this implies that additional module-scale studies are required to optimize local focusing methods and their synergy with device-level modifications to produce advanced photovoltaics.
关键词： quasi-Fermi level control,module-level enhancements,energy conversion efficiency,Photovoltaic panels,crystalline Si solar cells,local focusing,polydimethylsiloxane,PERC solar cells
更新于2025-09-23 15:19:57
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Optimized Operation of Quantum-Dot Intermediate-Band Solar Cells Deduced from Electronic Transport Modeling
摘要： Study of the physics of quantum electronic transport has not tackled the problems raised by quantum-dot intermediate-band solar cells. Our study shows that this physics imposes design rules for the intersubband transition. We develop an analytical model that correctly treats, from a quantum point of view, the trade-off between the absorption, the recombination, and the electronic transport occurring in this transition. Our results clearly indicate that it is essential to control the transit rate between the excited state of the quantum dot and the embedding semiconductor. For that, we propose assuming the dot in a tunnel shell whose main characteristics can be obtained by a simple analytical formula. Moreover, we show that in a realistic case, the energy transition needs to be larger than only 0.27 eV to obtain a quasi-Fermi-level-splitting. This quite small value designates the quantum-dot solar cell as a serious candidate to be an efficient intermediate-band solar cell. This work gives a framework to design efficient intersubband transitions and opens new opportunities for quantum-dot intermediate-band solar cells.
关键词： quantum-dot,intersubband transition,electronic transport modeling,intermediate-band solar cells,quasi-Fermi-level-splitting
更新于2025-09-23 15:19:57
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Mechanical stress dependence of the Fermi level pinning on an oxidized silicon surface
摘要： A combination of micro-Raman spectroscopy and micro-XPS (X-ray photo-electron spectroscopy) mapping on statically deflected p-type silicon cantilevers is used to study the mechanical stress dependence of the Fermi level pinning at an oxidized silicon (001) surface. With uniaxial compressive and tensile stress applied parallel to the ?110? crystal direction, the observations are relevant to the electronic properties of strain-silicon nano-devices with large surface-to-volume ratios such as nanowires and nanomembranes. The surface Fermi level pinning is found to be even in applied stress, a fact that may be related to the symmetry of the Pb0 silicon/oxide interface defects. For stresses up to 240 MPa, an increase in the pinning energy of 0.16 meV/MPa is observed for compressive stress, while for tensile stress it increases by 0.11 meV/MPa. Using the bulk, valence band deformation potentials the reduction in surface band bending in compression (0.09 meV/MPa) and in tension (0.13 meV/MPa) can be estimated.
关键词： Mechanical stress,Raman spectroscopy,X-ray photoelectron spectroscopy,Surface Fermi level pinning,Silicon,Interface defect
更新于2025-09-19 17:15:36
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Potential energy shift of the Fermi level at plasmonic structures for light-energy conversion determined by graphene-based Raman measurements
摘要： Single layer graphene was used to determine the electrochemical potential of plasmonic nano-structures for photoelectrochemical energy conversions. From electrochemical Raman measurements of the graphene layer under near-infrared light, illumination has revealed the relationship between the photoenergy conversion ability and the Fermi level of the plasmonic structure. The determination is based on in situ monitoring of G and 2D Raman bands of the graphene layer on plasmonic structures. The correlation plots of G and 2D bands show the dependence on the photoconversion ability. The present electrochemical Raman measurements provide detailed understanding of the plasmon-induced charge transfer process for further developments on the ability.
关键词： plasmonic structures,Raman measurements,graphene,Fermi level,photoelectrochemical energy conversion
更新于2025-09-19 17:13:59
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Optimization of SnO2-based electron-selective contacts for Si/PEDOT:PSS heterojunction solar cells
摘要： Tin oxide (SnO2) is a potentially excellent electron-selective contact (ESC) for silicon (Si)-based solar cells due to its satisfactory energy band structure and good crystallinity. However, unsatisfactory electron extraction ability and limited surface passivating effect of SnO2 ESCs will limit the performance of corresponding solar cells. We increase the Fermi level of SnO2 by doping Ethylene diamine tetraacetic acid (EDTA), which endows EDTA-SnO2 better electron extraction ability than SnO2. Moreover, EDTA-SnO2/SiOx bilayer ESC prepared by combining a EDTA-SnO2 layer and a thin silicon oxide (SiOx) film provides better surface passivation than EDTA-SnO2 ESC without impairing the charge transport capability markedly. The planar Si/PEDOT:PSS heterojunction solar cells (HSCs) with EDTA-SnO2/SiOx bilayer ESCs exhibit a power conversion efficiency (η) of 11.52%, which improves 13.7% in comparison with the η (10.13%) of HSCs with SnO2 ESCs, mainly caused by the increase in Voc and FF by 18 mV and 5.4% respectively.
关键词： Tin oxide,Electron-selective contact,Surface passivation,Silicon heterojunction solar cells,Fermi level
更新于2025-09-16 10:30:52
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Cd(Zn, S)Se quaternary thin films for electrochemical photovoltaic cell application
摘要： In this study, Cd1?xZnxSySe1?y (0 ≤ x = y ≤ 0.35) photoelectrodes are deposited via inexpensive facile chemical bath deposition. The effects of Zn and S doping on the compositional, microstructural, electrical, and optical properties of thin films were analysed. The electrochemical photovoltaic (EPV) cell of configuration Cd1?xZnxSySe1?y/0.25M sulfide/polysulfide/C was assembled to examine the different performance parameters in light and in dark conditions. An EPV cell fabricated with the Cd1?xZnxSySe1?y (0 ≤ x = y ≤ 0.075) photoelectrode exhibited a maximum photoconversion efficiency of 3.18%. This performance can be attributed primarily to the enhanced light-absorption ability of the material because of the enhanced rough microstructure and low recombination of photo-injected electrons with the electrolyte. The photovoltaic (PV) performance is significantly enhanced after doping CdSe with Zn and S.
关键词： EPV cells,hall effect,multinary materials,energy bandgap,electrostatic force microscopy,thin film electrodes,chalcogenide semiconductors,Fermi level
更新于2025-09-16 10:30:52
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Amide Additives Induced Fermi Level Shift for Improved Performance of Hole-Conductor-Free, Printable Mesoscopic Perovskite Solar Cells
摘要： Solution-processable organic-inorganic perovskite solar cells have attracted much attention in the past few years. Energy level alignment is of great importance for performance improvement of perovskite solar cells since it greatly influences charge separation and recombination processes. In this report, we introduce three amide additives, namely, formamide, acetamide, and urea into MAPbI3 perovskite by mixing them directly in perovskite precursor solutions. The Fermi level of MAPbI3 shifts from -4.36 eV to -4.63 eV, -4.65 eV and -4.61 eV respectively with these additives. The charge transfer between perovskite and mp-TiO2 is found to be promoted via TRPL spectra and the recombination process in perovskite is suppressed. As a result, the built-in electric field (Vbi) of the printable, hole-conductor-free mesoscopic perovskite solar cells based on these perovskites with amide additives is enhanced and a highest power conversion efficiency of 15.57% is obtained.
关键词： amide additives,Fermi level shift,printable mesoscopic perovskite solar cells
更新于2025-09-16 10:30:52
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Interfacial charge transfer between CsPbBr <sub/>3</sub> quantum dots and ITO nanoparticles revealed by single-dot photoluminescence spectroscopy
摘要： The interfacial charge transfer between single CsPbBr3 perovskite quantum dots (QDs) and indium tin oxide (ITO) is investigated by single-dot photoluminescence spectroscopy. It is found that when the Fermi level of single perovskite QDs aligns with that of ITO nanoparticles, the QD surface cannot be charged by the ITO through interfacial electron transfer. Therefore, the QD/ITO system with Fermi level alignments can exclude exciton nonradiative recombination processes involving the additional surface electrons, such as the exciton Auger recombination and the valence band hole transfer processes. Hence the photovoltaic devices based on perovskite QD/ITO system with the Fermi level alignments have the improved photoelectric conversion efficiency.
关键词： Fermi level alignments,single-dot photoluminescence spectroscopy,photoelectric conversion efficiency,interfacial charge transfer,CsPbBr3 quantum dots,ITO nanoparticles
更新于2025-09-11 14:15:04