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Correlation between the morphology and the opto-electronic and electrical properties of organometallic halide perovskite (CH<sub>3</sub>NH<sub>3</sub>MH<sub>3</sub>) thin films
摘要： Organometallic halide perovskites are emerging as a promising class of materials for optoelectronic applications. Crystal morphology is important for improving the organic-inorganic lead halide perovskite semiconductor property in optoelectronic, electrical and photovoltaic devices. It is thus important to investigate how the changes in crystal morphology affect the semiconductor behavior. This work presents a study that was carried out to assess the relationship between different deposition methodologies and the opto-electronic and electrical properties of the resultant organometallic halide perovskite thin films. Herein, single step solution deposition method and two step solution deposition methods have been used to deposit perovskite thin films. The structure and morphology of perovskite was controlled by changing concentration, annealing temperatures and dip coating times. From the study, prepared films showed different morphologies as the concentration, annealing temperatures and dip coating times were varied. Optical band gap energies of 2.23 eV, 2.13 eV and 2.09 eV were obtained for samples prepared by single step solution deposition method and 1.57 eV, 1.55 eV and 1.52 eV for two step solution deposition method. The sheet resistance values decreased with an increase in concentration, annealing temperatures and dip coating times. The decrease in optical band gap energy and sheet resistances are excellent properties for high performance photovoltaic devices.
关键词： Perovskite,sheet resistivity,activation energy,band gap,sheet resistance,spectroscopy
更新于2025-11-19 16:56:35
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A method to extend wavelength into middle-wavelength based on InAsSb/(Al)GaSb interband transition quantum well infrared photodetector
摘要： A method to extend the operating wavelength of the interband transition quantum well photodetector from extended short-wavelength IR to middle-wavelength infrared has been introduced. In the modified InAsSb quantum well, GaSb is replaced with AlSb/AlGaSb, the valence band of barrier material is lowered, the first restricted energy level (E1) is higher than the valence band of barrier material, the energy band structure forms type-II structure. The photocurrent spectral manifested that the fabricated photodetector exhibited a response range from 1.9 μm to 3.2 μm with two peaks at 2.18 μm and 3.03 μm at 78 K.
关键词： energy band calculation,InAsSb/AlSb/AlGaSb quantum well,interband transition,photodetector
更新于2025-09-23 15:21:01
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Dielectric Properties of Pulsed Laser Deposited Nanoscale CeNi5 Thin Films
摘要： Dielectric properties of pulsed laser deposited, nanoscale CeNi5 alloy layers, on glass or SiO2 substrate are described using the complex dielectric function. The UV–Vis–NIR spectral behavior of this function is studied separately for its real part ε1 (the dielectric constant or dielectric permittivity), and for its imaginary part ε2 (the dielectric loss function). The layers were obtained from grinded CeNi5 bulk powder using short, modulated laser pulses. The absolute reflectance of the obtained nanoscale alloy layers was measured at the 632.8 nm wavelength of a liquid nitrogen cooled and stabilized He–Ne source. This value was further used to renormalize the relative differential reflectance spectroscopy measurements performed in the UV?Vis?NIR domain. The obtained absolute reflectance spectra were processed using the Kramers–Kr?nig formalism, so that the real and imaginary parts of the complex dielectric function could be computationally determined, also leading to the calculation of the electron loss functions –Im ε–1 and –Im(1 + ε)–1. The behavior of these functions near the spectral inflexion points was determined using appropriate theoretical considerations. The variation of the dielectric functions was explained, electron density of states and the shape of the energy bands were inferred. This study reveals the layer thickness and deposition substrate dependent optical and electrical properties of the produced nanoscale CeNi5 structures.
关键词： dielectric constant,nanoscale CeNi5 thin films,dielectric loss function,pulsed laser deposition,electron energy band structures
更新于2025-09-23 15:21:01
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Textural and electro-optical study of a room temperature nematic liquid crystal 4ì?-pentyl-4-biphenylcarbonitrile doped with metal oxide nanowires in planar and in-plane switching cell configurations
摘要： This work shows the doping effect of metal oxide nanowires (alumina nanowires) on the textural and electro-optical characteristics of nematic liquid crystal (5CB) in planar and in-plane switching (IPS) cell configurations. Results indicate the increase in nematic to isotropic phase transition temperature after doping in both planar and IPS cells. A decrease in threshold voltage in addition to increase in contrast ratio, birefringence, and band gap energy was observed after doping with alumina nanowires in both types of cells. Overall analysis shows that IPS cell configuration has more improved threshold voltage and contrast ratio in addition to decrease in birefringence and transmission intensity, as compared to planar cell configuration. No effect of cell configuration was observed on energy band gap and found same value for both planar and IPS cell configurations, as energy band gap is a material specific property.
关键词： threshold voltage,Nematic liquid crystal,energy band gap,In-plane switching,nanowires
更新于2025-09-23 15:21:01
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Energy band alignment in molybdenum oxide/ Cu(In,Ga)Se2 interface for high efficiency ultrathin Cu(In,Ga)Se2 solar cells from low-temperature growth
摘要： In this work, the molybdenum oxide (MoOx) was employed as a back contact layer to improve the device performance of ultrathin Cu(In,Ga)Se2 (CIGS) solar cells with CIGS absorber synthesized through the low-temperature three-stage co-evaporation process. This contribution focuses on the investigation of the inherent mechanisms and the improved device performance in detail. Our research shows that the energy band of the CIGS/Mo interface can be tuned and the Schottky barrier can be reduced. Compared with the reference sample without MoOx, the back barrier height of the new device with 10 nm MoOx enjoys a significant decrease from 43.83 meV to 15.98 meV because of the improvement of energy band structure. Meanwhile, the results of wxAMPS simulation corroborate that the energy band bends upward in the devices with appropriate thickness of MoOx films, which facilitates the carrier transportation and suppresses the recombination of charge carriers at the MoOx/Cu(In,Ga)Se2 interface. Moreover, the carriers can transport through the MoOx/CIGS interface by tunneling when the MoOx film is thin enough. Finally, by controlling the thicknesses of MoOx films, an efficiency of 10.38 % is achieved in 0.5 μm CIGS solar cells by optimizing the MoOx thickness under the low-temperature three-stage co-evaporation process.
关键词： ultrathin,Cu(In,Ga)Se2,MoOx,low-temperature,energy band
更新于2025-09-23 15:19:57
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An analytical approach for modeling of high-efficiency crystalline silicon solar cells with homoa??hetero junctions
摘要： An analytical model based on charge neutrality principle and energy band diagram analysis is investigated to model a new structure of silicon heterojunction solar cell, which encompasses both homo and heterojunctions. In the analysed structure, a thin (pt)c-Si and a thin (nt)c-Si layers are used at front and back surfaces of (n)c-Si substrate respectively. The purpose of incorporating these layers is to reduce the solar cell output parameters sensitivity to a-Si:H/c-Si interface defect densities, increase the open circuit voltage eVocT and increase the fill factor (FFT. Since (n)c-Si silicon bulk becomes quasi neutral in the mentioned structure, charge neutrality equation can be separated as two independent equations for front and back surfaces. Solving charge neutrality equations, result in a-Si:H/c-Si interface potential, and subsequently charge concentration, electric field, surface recombination velocity, and open circuit voltage (Voc) calculation. Then, by adjusting doping concentration of the two additional layers, their effect on surface potential and energy band bending is studied. It is observed that (cid:0) 3, the Voc drops by when doping concentration of (pt)c-Si layer is increased from 1 ? 1018cm 15mV, and FF increases by 2:5%, while Voc and FF sensitivity to interface defects density is improved considerably. On the other hand, by (nt)c-Si layer insertion at back surface, in addition to decreasing sensitivity to interface defect densities in comparison to conventional SHJ silicon solar cell, Voc and FF are increased due to combination of high conductivity and enhancement of field effect passivation at back surface of solar cell. (cid:0) 3 Voc and FF Moreover, when doping concentration of (nt)c-Si layer increases from 1 ? 1018cm increases from 680 mV and 71% to 740 mV and 82% respectively.
关键词： HHJ silicon solar cell,(nt)c-Si layer,(pt)c-Si layer,Energy band diagram analysis,Charge neutrality principle
更新于2025-09-23 15:19:57
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Comparative studies on polarisability, and optical properties of BiZnBo–SLS and PbZnBo–SLS glass
摘要： Soda Lime Silica (SLS), mainly composed of SiO2, was utilised in this study as the source of SiO2 for fabrication of glass. A study of physical and optical properties was performed for the glass system of x [RmOn] (0.50?x) [ZnO] 0.20 [B2O3] 0.30 [SLS], where RmOn are Bi2O3 and PbO with x = 0.05, 0.10, 0.20, 0.30, 0.40, and 0.45 mol. The glass was prepared by melt-quenching method. Optical properties of the glass samples were obtained using UV–visible absorption measurements. The main objective of this study was to compare the structural, polarizability, and optical properties of these two series synthesized silica based glass. The structure of the glass system was determined by X-ray diffraction (XRD). The density and molar volume were found to increase as Bi2O3 and PbO concentration increased. The optical band gap, Eopt values for bismuth glasses were between 2.58 and 2.92 eV and varied from 2.42 to 2.92 eV for lead glasses. The highest concentration of Bi2O3 and PbO in glass system showed the smallest Eopt. Bi2O3 glass exhibit the significant value towards direct or indirect band gap in optoelectronic field compared to PbO glass. Refractive index of glass samples was measured by UV–visible spectrophotometer. The value lay between 2.42 and 2.52 for bismuth glass and 2.42 and 2.57 for lead glass and the value increased as bismuth ion (Bi3+) and lead ion (Pb2+) concentration increased. Metallisation criterion was investigated on the basis of refractive index and band gap. The metallisation criterion of the glass sample linearly decreased with increasing concentration of bismuth and lead ions as a result of increasing number of refractive indices and decreasing number of band gap energy. The positive value of metallisation criterion indicates that the glass materials are insulators or not metallic. In conclusion, the obtained results show that the addition of bismuth oxide in silica glass improved its structural and optical properties compared to lead glass.
关键词： UV–visible,Polarizability,Refractive index,Metallisation criterion,Energy band gap
更新于2025-09-19 17:15:36
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Fabrication of Pure Sb2S3 and Fe (2.5%): Sb2S3 Thin Films and Investigation Their Properties
摘要： Pure Sb2S3 and Fe (2.5%): Sb2S3 thin films were synthesized on Zn2SnO4 coated with FTO conductive glasses using chemical bath deposition (CBD) technique. The X-ray diffraction (XRD) patterns obtained show that both thin films have an orthorhombic structure. Although the crystal structure of the two thin films was the same, the crystalline size of Fe (2.5%): Sb2S3 thin film (51.15 nm) was found to be smaller than that of pure Sb2S3 (52.89 nm). The effect of Fe-doped metal on crystal size of Sb2S3 was observed with this result. Another important observation is that the energy band gap of Fe (2.5%): Sb2S3 thin film (2.00 eV) is larger than that of pure Sb2S3 (1.89 eV). The photovoltaic properties of the synthesized thin films were examined by applying both incident photon-to-current efficiency (IPCE) and current density (J)–voltage (V) measurements. The obtained IPCE(%) values at 600 nm for pure Sb2S3 and Fe (2.5%): Sb2S3 thin films are 30.29 and 49.06, respectively. Using the J–V curves, the calculated η (%) values for pure Sb2S3 and Fe (2.5%): Sb2S3 thin films are 3.95 and 5.44, respectively. Based on the data obtained from both measurements, it was observed that the Fe dopant significantly enhance the performance of the Sb2S3-based solar cell devices.
关键词： Doping,Photovoltaic,Thin film,Particle size,Energy band gap,Synthesis
更新于2025-09-19 17:15:36
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Realizing Stable Artificial Photon Energy Harvesting Based on Perovskite Solar Cells for Diverse Applications
摘要： As the fastest developing photovoltaic device, perovskite solar cells have achieved an extraordinary power conversion efficiency (PCE) of 25.3% under AM 1.5 illumination. However, few studies have been devoted to perovskite solar cells harvesting artificial light, owing to the great challenge in the simultaneous manipulation of bandgap-adjustable perovskite materials, corresponding matched energy band structure of carrier transport materials, and interfacial defects. Herein, through systematic morphology, composition, and energy band engineering, high-quality Cs0.05MA0.95PbBrxI3?x perovskite as the light absorber and NbyTi1?yO2 (Nb:TiO2) as the electron transport material with an ideal energy band alignment are obtained simultaneously. The theoretical-limit-approaching record PCEs of 36.3% (average: 34.0 ± 1.2%) under light-emitting diode (LED, warm white) and 33.2% under fluorescent lamp (cold white) are achieved simultaneously, as well as a PCE of 19.5% (average: 18.9 ± 0.3%) under solar illumination. An integrated energy conversion and storage system based on an artificial light response solar cell and sodium-ion battery is established for diverse practical applications, including a portable calculator, quartz clock, and even environmental monitoring equipment. Over a week of stable operation shows its great practical potential and provides a new avenue to promote the commercialization of perovskite photovoltaic devices via integration with ingenious electronic devices.
关键词： energy band engineering,weak light harvesting,perovskite solar cells,indoor application
更新于2025-09-19 17:13:59
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Analysis of Defects and Surface Roughness on the Hydrogenated Amorphous Silicon (a-Si:H) Intrinsic Thin Film for Solar Cells
摘要： Effect of defect - through observation of energy absorption Urbach, on deposition rate, energy band gap, and surface roughness of intrinsic thin film are investigated using Radio Frequency Plasma Enhance Chemical Vapor Deposition (RF-PECVD). Films are grown on ITO (Indium Tin Oxide) glass substrate. Analysis of energy band gap is conducted to determine changes in the structure of a thin film of a-Si:H. Energy band gap is important to determine the portion of the spectrum of sunlight that is absorbed solar cells. From the characterization using UV-Vis spectrometer and the Tauc’s plot method, the width of the resulting energy band gap is greater if the hydrogen dilution is increased. It can be shown that the increase of the hydrogen dilution, will increase the energy band gap, and the surface roughness of thin layers. Instead, the improvement of the hydrogen dilution decrease the rate of deposition and Urbach energy. It is estimated that with greater hydrogen dilution, an intrinsic thin film of a-Si:H is more conductive for more reduction in residual of band tail defects or dangling bond defects.
关键词： RF-PECVD,a-Si:H,Energy band gap,Urbach energy,Hydrogen dilution
更新于2025-09-16 10:30:52