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Investigation of valence plasmon excitations in GMZO thin film and their suitability for plasmon-enhanced buffer-less solar cells
摘要： The approach of eliminating buffer layer in conjunction with plasmon-enhanced transparent conduction oxide (TCO) layer is an attractive methodology to realize low-cost ultrathin buffer-less solar cells (SCs) by introducing plasmon-enhanced absorption and reduced fabrication steps. Here, we report a novel method to generate wide-band sputter-stimulated plasmonic feature in Ga-doped-MgZnO (GMZO) thin-films, which are observed due to the different metallic and metal-oxide nanoclusters formation. Through an extensive analysis of photoelectron spectroscopy, spectroscopic ellipsometry, and field-emission scanning electron microscope measurements the evaluation of plasmonic features and correlation of them with various nanoclusters inside GMZO thin-film is performed. Additionally, the suitability and expected performance of plasmon-enhanced GMZO thin-film based buffer-less SCs are probed through; 1) band-offset analysis at the plasmon enhanced-GMZO/CIGSe heterojunction; 2) simulation studies to analyze the effect of conduction band-offset (CBO) on the performance of the buffer-less SCs; 3) predicting the performance of the buffer-less SC using the parameters of GMZO thin-films with varying CBO, and 4) envisaging the concept of ultrathin buffer-less SC with calculated CBO and absorber layer thickness (300 nm) for ultrathin SCs. Moreover, at the experimentally calculated band-offset with ultrathin absorber layer thickness (300 nm), theoretically calculated buffer-less SC performance parameters estimated to be open-circuit voltage (Voc): 0.75 V, short-circuit current density (Jsc): 17.29 mA/cm2, fill-factor (FF): 80.5%, and efficiency (Eff): 10.46%.
关键词： Ultrathin solar cells,UPS,CIGSe,Plasmons
更新于2025-11-21 11:03:13
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Investigation of valence electron excitation and plasmonic enhancement in sputter grown NMZO thin films: For energy harvesting applications
摘要： We report a novel approach of sputter-stimulated plasmonic generation in Na-doped MgZnO (NMZO) thin films. Sputtering of material during film growth by utilizing secondary direct-coupled ion-source present in dual-ion beam sputtering system leads to the generation of nanoclusters of its constituent elements due to different sputtering-out rates of various elements present in the films. The authentication of plasmonic generation in NMZO is conducted as follows a) identification of plasmonic signature in electron energy loss spectra obtained by ultraviolet photoelectron spectroscopy measurement, b) valence bulk, valence surface, and particle plasmon resonance energy calculations are performed, and each plasmon peak is indexed with corresponding plasmon energy peak of different nanoclusters, and c) spectroscopic ellipsometric measurement is deployed to verify plasmonic behavior by investigating different optical properties. Additionally, incorporation of the plasmonic feature along with alkali metals plays a crucial role in the improvement of the performance of solar cells. Therefore, plasmon enhanced NMZO as a backscattering layer in between CIGSe/back contact is probed to ascertain the additional benefits of 1) Na incorporation into the absorber layer as a result of the Na diffusion from the NMZO layer, and 2) improvement in the morphology of the CIGSe thin film with the incorporation of NMZO layer in between the back-contact and CIGSe. The diffusion of Na into the absorber layer is probed by deploying secondary ion mass spectroscopy measurements, and improvement in the morphology of CIGSe with the incorporation of NMZO layer between the back-contact/absorber is investigated using field-emission scanning electron microscope analysis.
关键词： UPS,NMZO,Ultrathin solar cells,Plasmons,Sputtered
更新于2025-11-21 11:03:13
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Band Alignment of the CdS/Cu <sub/>2</sub> Zn(Sn <sub/>1-x</sub> Ge <sub/>x</sub> )Se <sub/>4</sub> Heterointerface and Electronic Properties at the Cu <sub/>2</sub> Zn(Sn <sub/>1-x</sub> Ge <sub/>x</sub> )Se <sub/>4</sub> surface: x = 0, 0.2, 0.4
摘要： The surface electronic properties of the light absorber and band alignment at the p/n heterointerface are key issues for high performance heterojunction solar cells. We investigated the band alignment of the heterointerface between cadmium sulfide (CdS) and Ge incorporated Cu2ZnSnSe4 (CZTGSe), with Ge/(Ge+Sn) ratios (x) between 0 and 0.4, by X-ray photoelectron, ultra-violet, and inversed photoemission spectroscopies (XPS, UPS, and IPES, respectively). In particular, we used interface-induced band bending in order to determine the conduction-band offset (CBO) and valence-band offset (VBO), which were calculated from the core-level shifts of each element in both the CdS overlayer and the CZTGSe bottom layer. Moreover, the surface electronic properties of CZTGSe were also investigated by laser-irradiated XPS. The CBO at the CdS/CZTGSe heterointerface decreased linearly, from +0.36 to +0.20 eV, as x was increased from 0 to 0.4; in contrast, the VBO at the CdS/CZTGSe heterointerface was independent of Ge content. Both UPS and IPES revealed that the Fermi level at the CZTGSe surface is located near the center of the bandgap. The hole concentration at the CZTGSe surface was of the order of 1011 cm-3, which is much smaller than that of the bulk (~1016 cm-3). We discuss the differences in hole deficiencies near the surface and in the bulk on the basis of laser-irradiated XPS, and conclude that hole deficiencies are due to defects distributed near the surface with densities that are lower than in the bulk, and the Fermi level is not pinned at the CZTGSe surface.
关键词： Solar cell,Kesterite,IPES,XPS,Band alignment,CZTGS,UPS
更新于2025-09-23 15:23:52
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Electronic structure and magnetic behaviors of exfoliated MoS<sub>2</sub> nanosheets
摘要： The correlation of electronic structure and magnetic behaviors of layered molybdenum disulfide (MoS2) nanosheets, mechanically exfoliated from pristine hexagonal crystal (2H-MoS2) have been studied. Raman spectra show the energy difference (ΔE) between two Raman peaks A1g and E12g was about 20.2 cm-1, indicating the formation of mono-/bi-layered MoS2 nanosheets as obtained after mechanical exfoliation from pristine 2H-MoS2. The absence of the reflection peak (002) in X-ray diffraction patterns confirms the formation of few-layered and mono-/bi-layered MoS2 nanosheets. Mo LII-edge and S K-edge X-ray absorption near edge structure spectra of mono-/bi-layered MoS2 nanosheets show the splitting of different peaks that cause a noticeable change in their band structure. Magnetic M-H hysteresis loops measurement clearly demonstrates the increase of room temperature ferromagnetism from pristine to mono-/bi-layer MoS2, due to the existence of defects (“S”- vacancies or defects at the grain boundaries region) and the increase of DOS. UPS (He-I) measurements show the valence band maximum position increased from 1.11 eV (pristine MoS2) to 1.57 eV (mono-/bi-layered MoS2 nanosheets), whereas the surface work function (Ф) reduced from 4.85 eV (pristine MoS2) to 4.47 eV (mono-/bi-layered MoS2 nanosheets). UPS (He-II) valence band density of states (DOS) of S 3p - derived states near Fermi level (Ef). Mo 3d and S 2p XPS core level peaks shifted to higher energy with the reduction of the number of layers in exfoliated MoS2. As the number of layers decreased, valence band spectra, as well as VB-PES spectra of mono-/bi-layered MoS2 nanosheets, exhibits an enhanced DOS with reduced thickness.
关键词： UPS,VB-PES,XANES,Exfoliated MoS2-nanosheets,XPS,RT-FM
更新于2025-09-23 15:22:29
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The electronic band structure analysis of OLED device by means of in situ LEIPS and UPS combined with GCIB
摘要： Low-energy inverse photoelectron spectroscopy (LEIPS) and ultraviolet photoelectron spectroscopy (UPS) incorporated into the multitechnique XPS system were used to probe the ionization potential and the electron affinity of organic materials, respectively. By utilizing gas cluster ion beam (GCIB), in situ analyses and depth profiling of LEIPS and UPS were also demonstrated. The band structures of the 10-nm-thick buckminsterfullerene (C60) thin film on Au (100 nm)/indium tin oxide (100 nm)/glass substrate were successfully evaluated in depth direction.
关键词： LEIPS–UPS,GCIB depth profile,OLED device,electronic band structure
更新于2025-09-23 15:21:01
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Modification of Hole Transport Layers for Fabricating High Performance Nona??fullerene Polymer Solar Cells
摘要： Interfacial engineering is expected to be a feasible strategy to improve the charge transport properties of the hole transport layer (HTL), which is of crucial importance to boosting the device performance of organic solar cells (OSCs). In this study, two types of alcohol soluble materials, 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4-TCNQ) and di-tetrabutylammoniumcis–bis(isothiocyanato)bis(2,2’-bipyridyl-4,4’-dicarboxylato) ruthenium (II) (N719) dye were selected as the dopant for HTL. The doping of F4-TCNQ and N719 dye in poly(ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) with and without integrating a graphene quantum-dots (G-QDs) layer has been explored in poly[[2,6′-4-8-di(5-ethylhexylthienyl)benzo[1,2-b:3,3-b]dithiophene][3-fluoro-2[(2-ethylhexyl)carbonyl]thieno[3,4-b]thio-phenediyl:(2,2′-((2Z,2′Z)-(((4,4,9,9-tetrakis(4-hexylphenyl)-4,9-dihydro-s-indaceno[1,2-b:5,6-b′]dithiophene-2,7-diyl)bis(4-((2-ethylhexyl)oxy)thiophene-5,2-diyl))bis(methanylylidene))bis(5,6-difluoro-3-oxo-2,3-dihydro-1H-indene-2,1-diylidene))dimalononitrile (PTB7-Th:IEICO-4F) OSCs. The power conversion efficiency of the non-fullerene OSCs has been increased to 10.12% from 8.84%. The influence of HTL modification on the nano-morphological structures and photophysical properties is analyzed based on the comparative studies performed on the control and modified devices. The use of chemical doping and bilayer strategy optimizes the energy level alignment, nanomorphology, hole mobility, and work-function of HTL, leading to considerable reduction of the leakage current and recombination losses. Our work demonstrates that the doping of HTL and the incorporation of G-QDs layer to constitute a bilayer HTL is an promising strategy to fabricate high performance non-fullerene polymer solar cells.
关键词： UPS,PTB7-Th:IEICO-4F,atomic force microscopy,XPS,Organic solar cells
更新于2025-09-23 15:21:01
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Energy level alignment and nanoscale investigation of a-TiO <sub/>2</sub> /Cu-Zn-Sn-S interface for alternative electron transport layer in earth abundant Cu-Zn-Sn-S solar cells
摘要： Efficiency of earth abundant and pure sulfide kesterite Cu-Zn-Sn-S (CZTS) solar cell has been stagnant around 9.4% for years, while its counterpart Cu-In-Ga-Se (CIGS) reports an efficiency of more than 22%. Low open circuit voltage (VOC) is the major challenging factor for low efficiency due to severe nonradiative interface recombinations. The existence of higher defect states at the conventional CZTS-CdS interface due to undesirable energy level alignment and lattice misfit promotes trap-assisted recombinations and results in low VOC. In this work, amorphous TiO2 (Eg = 3.8 eV) is proposed as a promising substitute to the conventional and low bandgap CdS (Eg = 2.4 eV) layer. The surface and interface of the CZTS-TiO2 layer were investigated using X-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS). The result reveals favorable "spike"-like conformations at the CZTS-TiO2 interface with a conduction band offset value of 0.17 eV. The nanoscale probing of the interface by Kelvin probe force microscopy across CZTS-TiO2 layers shows a higher potential barrier for interface recombination at CZTS-TiO2 in contrast to the conventional CZTS-CdS interface. Finally, the fast decay response and lower persistent photoconductivity of photogenerated carriers for CZTS-TiO2 heterojunction based photodetectors further validate our results. The energy level alignment and nanoscale interface studies signify TiO2 as a promising alternate buffer layer for earth abundant CZTS solar cells.
关键词： XPS,TiO2,CZTS,CdS,energy level alignment,KPFM,UPS,solar cells,interface recombination
更新于2025-09-16 10:30:52
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A Reconfigurable Solar Photovoltaic Grid-Tied Inverter Architecture for Enhanced Energy Access in Backup Power Applications
摘要： In this paper, a photovoltaic (PV) reconfigurable grid-tied inverter (RGTI) scheme is proposed. Unlike a conventional GTI that ceases operation during a power outage, the RGTI is designed to act as a regular GTI in the on-grid mode but it is reconfigured to function as a DC-DC charge-controller that continues operation during a grid outage. During this period, the RGTI is tied to the battery-bank of an external UPS based backup power system to augment it with solar power. Such an operation in off-grid mode without employing high-bandwidth communication with the UPS is challenging, as the RGTI control must not conflict with the battery management system of the UPS. The hardware and control design aspects of this requirement are discussed in this paper. A battery emulation control scheme is proposed for the RGTI that facilitates seamless functioning of the RGTI in parallel with the physical UPS battery to reduce its discharge current. A system-level control scheme for overall operation and power management is presented to handle the dynamic variations in solar irradiation and UPS loads during the day, such that the battery discharge burden is minimized. The design and operation of the proposed RGTI system are independent of the external UPS and can be integrated with an UPS supplied by any manufacturer. Experimental results on a 4 kVA hardware setup validate the proposed RGTI concept, its operation and control.
关键词： Solar PV,Battery,Grid-tied Inverters,dual-mode inverters,UPS,Closed-loop control
更新于2025-09-12 10:27:22
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Valance band properties of MgZnO thin films with increasing Mg content; phase separation effects
摘要： Mg alloyed ZnO thin films up to 30 % Mg was grown on glass substrate by spray pyrolysis method. Phase separation has been significant in 30% Mg and barely observable 20% Mg incorporated thin films. PL measurements have displayed two emissions in ZnO thin films at energy of 3.26 eV and 2.10 eV which shifts to higher energy by the Mg incorporation. Similarly, bandgap widening in MgZnO thin films has been observed up to 3.71 eV in 15% Mg incorporated thin film. The widening of the band gap has not been followed for the thin films showing phase separation. Valance band maximum (VBM) positions relative to the Fermi level has been measured by UPS and no significant variation according to the vacuum level has been observed. On the other hand, Fermi level gets close to the VBM as the Mg content increases in the thin films.
关键词： MgZnO,XPS on MgZnO,valance band maximum positions in MgZnO,UPS on MgZnO
更新于2025-09-11 14:15:04