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Performance evaluation of composition graded layer of aSi1-xGex: H in n+aSi:H/i-aSi:H/p+aSi1-xGex:H graded band gap single junction solar cells
摘要： The work investigates the role of composition grading of amorphous silicon germanium alloy on single junction graded band gap amorphous silicon solar cells, for the first time. The fabrication and optical characterization of composition graded aSi1-xGex: H alloy by varying the gas flow rate of germane (GeH4) are presented. We propose the composition graded p+aSi1-xGex: H layer to be considered as one of the active layers in amorphous silicon based solar cells. The principle of operation of the solar cell is illustrated with the energy band diagram of proposed n+aSi:H/i-aSi:H/p+aSi1-xGex:H solar cell structure. Further, the behavior of the structure is evaluated through simulation in terms of proposed layer thickness variation and temperature variation. It is observed that the proposed structure is capable of delivering an open circuit voltage (V oc), short circuit current density (Jsc), Fill Factor (FF) and conversion efficiency (g) of 1.1 V, 15.56 mA/cm2, 0.885 and 15.19% respectively, which is at par with any other single junction amorphous silicon solar cells. The cell performance parameters were compared with related state of the art as well as our previous works. The performance parameters of proposed structure show that it is better to use a single composition graded layer instead of using a number of non-graded composition layers in photovoltaic structures, which reduces complexity and cost of fabrication.
关键词： Internal Quantum Efficiency,Optical band gap,Germane flow rate,Conversion efficiency,Composition grading,PECVD
更新于2025-09-12 10:27:22
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Optical Characterization of III-V Multijunction Solar Cells for Temperature-Independent Band Gap Features
摘要： A recently developed method to characterize the band gap energies of III-V optosemiconductors was utilized to determine temperature-invariant band gap features of multijunction solar cells. The method is based on measuring electroluminescent spectra of the solar cells at different temperatures. The normalized spectra reveal temperature-invariant energy values of the different junctions which are further converted to band gap energies. The method utilization requires a calibrated spectroradiometer and a temperature controlled mounting base for the solar cell under test, however, no knowledge about the absolute temperature of the cell under measurement. The method was tested on GaAs and GaInP solar cells that consist of single and dual junctions. The band gap energies were also derived from spectral response measurements. The differences of the determined band gap energies from the literature values were smaller than 1.1%. Compared with other band gap determination methods, the developed method yields temperature-invariant band gap characteristics; with a known uncertainty, that separated the different junctions in a multijunction device without individual biasing for the different junctions. In addition, a temperature-independent characterization parameter ensures that the operating conditions of the device under test do not affect the results.
关键词： III-V solar cells,light-emitting diode (LED),spectral response,temperature,Band gap
更新于2025-09-12 10:27:22
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Effect of deep UV laser treatment on silicon-doped Tin oxide thin film
摘要： In this paper, the effect of deep ultraviolet (UV) laser on physical and electrical properties of amorphous Silicon‐doped tin oxide (amorphous Si‐Sn‐O, a‐STO) thin films were studied. Surface morphology, thickness, crystallinity, and optical band gap of a‐STO thin films treated by laser were investigated. Results showed that the decrease of thickness and surface roughness of a‐STO thin films after deep UV laser treatment, and the films maintained an amorphous structure, which implied that the quality of a‐STO thin films were improved. The peak position of oxygen vacancy binding energy became lower; this is caused by an increase in oxygen vacancies resulting in a decrease in coordination number. And the oxygen vacancy content of the a‐STO thin films was increased after deep UV laser treatment. In addition, the optical band gap of a‐STO films was broaden after the deep UV laser treatment. It exploits a new application of deep UV laser in oxide semiconductor.
关键词： oxygen vacancy,amorphous STO thin film,optical band gap,deep ultraviolet laser
更新于2025-09-12 10:27:22
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Strain Effects on the Band Gap and Diameter of CdSe Core and CdSe/ZnS Core/Shell Quantum Dots at Any Temperature
摘要： We present the results of an experimental study about strain effects on the core band gap and diameter of spherical bare CdSe core and CdSe/ZnS core/shell quantum dots (QDs) synthesized by using a colloidal technique at varying temperatures. Structural characterizations were made by using X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) techniques. Optical characterizations were made by using UV-Vis absorption and fluorescence emission spectroscopies. The XRD analysis suggests that the synthesized bare CdSe core and CdSe/ZnS core/shell QDs have zinc blende crystal structure. HRTEM results indicate that the CdSe core and CdSe/ZnS QDs have average particle sizes about 3.50 nm and 4.84 nm, respectively. Furthermore, compressive strain causes an increase (decrease) in the core band gap (diameter) of spherical CdSe/ZnS core/shell QDs at any temperature. An elastic strain-modified effective mass approximation (EMA) predicts that there is a parabolic decrease (increase) in the core band gap (diameter) of QDs with temperature. The diameter of spherical bare CdSe core and CdSe/ZnS core/shell QDs calculated by using the strain-modified EMA, with core band gap extracted from absorption spectra, are in excellent agreement with the HRTEM data.
关键词： diameter,quantum dots,band gap,CdSe,strain effects,CdSe/ZnS,temperature
更新于2025-09-12 10:27:22
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New Aspect for Band Gap Energy of Graphene-Mg2CuSnCoO6-Gallic Acid as Counter-Electrode for Enhancing Dye-sensitized Solar Cell Performance
摘要： To develop counter-electrodes (CEs) for dye-sensitized solar cells (DSSCs), band gap energy of quaternary semiconductor materials is of great interest. In the present study, a novel graphene sheet based on Mg2CuSnCoO6-Gallic acid nanomaterials (G/MCS@Gallic) was modified with a new Joule heating method and a laser was applied for measuring band gap energy. Synergistic effect between graphene and Mg2CuSnCoO6-Gallic ensured excellent electron transport through the electrode and low band gap energy. The large surface area of the hybrid graphene materials rivaled the catalytic capability for iodide reduction. DSSCs achieved a maximum photoelectric conversion efficiency of 13.30% based on 10% G/MCS@Gallic CE, which was higher than that of platinum conversion efficiency. Thus, G/MCS@Gallic provides a novel, inexpensive, high-performance, and flexible cathode for solar cell application.
关键词： Quaternary semiconductor,DSSCs,Laser Band gap,Joule heating method
更新于2025-09-12 10:27:22
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w-ZnO nanostructures with distinct morphologies: Properties and integration into dye sensitized solar cells
摘要： Herein, we report the cost-e?ective and single-step reaction strategies for the synthesis of distinct morphology of ZnO namely, nanoparticles, nanotubes and nanowires involving co-precipitation and hydrothermal methods. Powder X-Ray di?raction analysis indexed nine distinct peaks which correspond to the w-ZnO for all the synthesized nanostructures. The formation mechanism of nanostructures are proposed, in which the role of surfactants (polyvinylpyrrolidone and sodium dodecyl sulfate) and the oriented self-assembly are taken into account. The Raman spectral analysis of the nanostructures con?rms the presence of highly intense E2 high phonon vibrational modes corresponding to the movement of O-atoms and Zn sub-lattices of w-ZnO respectively. The prepared yellowish ZnO nanowires reveal intensi?cation in optical absorption and shrinkage in band gap due to increased oxygen vacancies in the sample. The quenching of green luminescence in the photo-luminescence spectrum of the nanowire further con?rms the oxygen vacancies. All the nanostructures were integrated into dye sensitized solar cells as photoanode materials. The photovoltaic parameters and electrochemical charge transfer properties of the fabricated dye sensitized solar cells (DSSCs) were evaluated by using photocurrent density-photovoltage curves and Nyquist plots of electrochemical impedance spectroscopic (EIS) studies. Due to the presence of large pore size in nanowires and nanotubes, the dye in?ltration and electrolyte di?usion rates are high and cause the highest photocurrent densities of 1.714 mA cm?2 and 1.813 mA cm?2 respectively. The speci?c hollow tube like nanostructures is channelizing the photo-injected electrons directly to the collector electrode and results in high photovoltaic conversion e?ciency of 1.109%. High value of charge transfer resistance across the ZnO/dye/electrolyte interfaces in nanocapsule and nanoparticle based DSSCs enforce low conversion e?ciency to the devices.
关键词： Growth mechanism,Band gap narrowing,Dye sensitized solar cells,Zinc oxide
更新于2025-09-12 10:27:22
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TaS <sub/>2</sub> Back Contact Improving Oxide-Converted Cu <sub/>2</sub> BaSnS <sub/>4</sub> Solar Cells
摘要： Solar cells based on the wide band-gap Cu2BaSnS4 (CBTS) photoabsorber have achieved open circuit voltages up to 1.1 V over a short development period, making CBTS an attractive material for tandem photovoltaic and photoelectrochemical cells. In this work, we explore an alternative CBTS growth route based on oxide precursors, and we propose TaS2 as an alternative back contact material to the commonly used Mo/MoS2. The oxide precursor route does not require higher sulfurization temperatures than other more common fabrication routes, and it yields CBTS films with negligible Stokes shift between photoluminescence maximum and band gap energy, while at the same time avoiding sulfur contamination of vacuum systems. The high work-function metallic TaS2 compound is selected as a prospective hole-selective contact, which could also prevent the losses associated with carrier transport across the semiconducting MoS2 layer. By comparing CBTS solar cells with Mo and TaS2 back contacts, the latter shows a significantly lower series resistance, resulting in a 10% relative efficiency improvement. Finally, we fabricate a proof-of-concept monolithic CBTS/Si tandem cell using a thin Ti(O,N) interlayer intended both as a diffusion barrier and as a recombination layer between the two subcells.
关键词： wide band gap absorber,back contact,kesterite,cation substitution,tandem solar cell,silicon,TaS2,sputtering
更新于2025-09-12 10:27:22
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Silicene Quantum Dots Confined in Few-Layer Siloxene Nanosheets for Blue Light-Emitting Diodes
摘要： Two-dimensional silicon-based materials have unique physical and chemical properties due to high surface area and quantum confinement effects. Herein, a topochemical reaction method is used for preparing silicene quantum dots confined in few layer siloxene nanosheets with FeCl3?6H2O as oxidant, which shows thickness less than 2 nm. The experimentally prepared siloxene nanosheets are dispersible, with silicene quantum dots having average diameter less than 5 nm. The silicene quantum dots are self-organized through the oxidation of FeCl3, showing unique optical properties of blue emission. The UV-visible absorption and PL emission spectra indicate the quasi-direct band gap transition to the emission. Besides, the few-layer siloxene nanosheets with silicene quantum dots have a radiative lifetime of 1.098 ns at an emission wavelength of 435 nm, which derives from the quasi-direct band transition of silicene quantum dots. Such two-dimensional nanosheets of silicon possess potential applications for the emitting layer materials of blue light-emitting diodes (LED).
关键词： topochemical reaction,silicene quantum dot,photoluminescence,siloxene,quasi-direct band gap
更新于2025-09-12 10:27:22
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Fabrication and performance of dye sensitized solar cell based on spin coated ZnS nanoparticles
摘要： ZnSx nanoparticles (NPs) with different ratios of sulfur, x = 0.5, 1 and 2, were prepared by solvothermal technique. The structural analyses, based on XRD and FTIR, show that for sulfur content x = 0.5 two phases were formed ZnS and ZnO NPs with cubic and hexagonal structure, respectively. While for sulfur content x = 1 and 2 only ZnS NPs with cubic structure was observed. The crystallites size was study before and after annealing at 500 °C. SEM images show that the prepared samples have nanocrystalline nature. Absorbance spectrum was used to calculate the optical band gap of the powder samples dispersed in potassium hydroxide solution. All samples have direct optical band gap which was inversely proportional to the sulfur content. ZnS NPs were irradiated by different doses of γ-rays and the effect on optical band gap was studied. The resulting from solvothermal preparation technique was served as precursor solution to deposit ZnSx layers onto the fluorine-doped tin oxide coated glass substrates by spinning process. The deposited ZnS NPs layers were successfully used as photoelectrode materials in dye-sensitized solar cells and the I–V characteristics were measured under illumination and in dark. An improvement in the efficiency was observed after annealing the ZnSx layers, x = 0.5 and 1, photoelectrode materials.
关键词： Dye-sensitized solar cells,Solvothermal technique,ZnS nanoparticles,γ-irradiation,Optical band gap
更新于2025-09-12 10:27:22
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Interaction of Graphene Quantum Dots with Oligothiophene: A Comprehensive Theoretical Study
摘要： Graphene/polythiophene composites are widely used in a variety of optoelectronic devices and applications, e.g., as electrode materials in capacitors and solar cells, but the detailed molecular-level relationship between their structural and electronic properties is not well understood. We present a density functional theory study of these composites using model systems consisting of graphene nanosheets and nanoribbons sandwiched between oligothiophenes (up to 13 monomers in length). These systems are investigated by computing optical band gaps, UV-vis spectra, densities of states, and by analyzing noncovalent interactions in terms of the reduced density gradient. Frontier molecular orbital analysis reveals a significant decrease in the optical band gap upon increasing the concentration of graphene, which can be tuned by adjusting the proportion of graphene using larger nanoribbons. This finding has implications for device design in these materials.
关键词： UV-vis Spectra,Composites,Optical Band Gap,Graphene,Noncovalent Interactions,Density Functional Theory,Polythiophene
更新于2025-09-12 10:27:22