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Impact of Hydrogen flow rate on physical properties of ZnS thin films: As potential buffer layer in solar cells
摘要： The exceptional need of potential Cd-free buffer layer in thin film solar cell devices motivated us to study the role of post-deposition Hydrogen annealing for the optimization of physical properties of ZnS thin films. The deposited films of thickness 200 nm were hydrogenated within the flow rate range of 50.0–150.0 sccm at 200°C. XRD analysis revealed transformation of amorphous into cubic phase with maximum crystallinity at 150.0 sccm for films deposited on glass substrate while into wurtzite structure for films on ITO substrate with enhanced crystallinity. A mixed phase (cubic and hexagonal) at 150.0 sccm also appeared. Electrical behaviour (I–V) exhibits ohmic nature with maximum carrier concentration at 100.0 sccm. The blue shift in absorption edge and maximum of 95% transmittance were recorded in the visible region with optical energy band gap of 3.41 eV at 150.0 sccm. The reduction in surface roughness is observed in surface topographical analysis while the photoluminescence (PL) study indicated a sharp peak at 2.95 eV with strongest emission for 150.0 sccm attributed to reduction of defects at interstitial sites and passivation of grain boundaries. These results are useful to understand the Hydrogen related impurities in ZnS films and the improvement caused by hydrogenation to physical properties suited for buffer layer in solar cells.
关键词： Buffer layer,ZnS thin films,Hydrogenation,Physical properties,e-beam evaporation
更新于2025-09-23 15:19:57
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Impact of Bi doping on CdTe thin films: Thermal annealing evolution of physical properties for solar cell absorber layer applications
摘要： To mitigate probability of instability and device degradation associated with traditional Cu doping and to tune required band gap as well as to reduce open circuit voltage loss to solar cell device, a study on evolution to the physical properties of Bi-doped CdTe films is reported. Thin films of CdTe:Bi 2% alloy are developed employing electron-beam deposition followed by air annealing. Structural studies reveal that films have preferred crystal growth along (111) plane and with annealing, films turned out to be polycrystalline. Absorbance of films is found to be affected with annealing where 450 °C annealed films show maximum absorbance. The current-voltage measurements show linear relationship reveal to ohmic contacts between the films and transparent conducting oxide substrate and conductivity is observed to be varied with annealing. The atomic force microscopy study indicates an increase in surface roughness with annealing (except for 300 °C). Our findings warrant that the optimized physical properties of CdTe:Bi 2% films annealed at 450 °C may play important role to enhance the solar cell device performance concerned.
关键词： Bismuth doping,Absorber layer,Air-annealing,Thin films,Cadmium telluride,Electron beam evaporation
更新于2025-09-23 15:19:57
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Superspreading and Drying of Trisiloxane-Laden Quantum Dot Nanofluids on Hydrophobic Surfaces
摘要： Nano?uids hold promise for a wide range of areas of industry. However, understanding the wetting behavior and deposition formation in the course of drying and spreading of nano?uids, particularly containing surfactants, is still poor. In this paper, the evaporation dynamics of quantum dot-based nano?uids and evaporation-driven self-assembly in nanocolloidal suspensions on hexamethyldisilazane-, polystyrene-, and polypropylene-coated hydrophobic surfaces have been studied experimentally. Moreover, for the very ?rst time, we make a step toward understanding the wetting dynamics of superspreader surfactant-laden nano?uids. It was revealed that drying of surfactant-free quantum dot nano?uids in contrast to pure liquids undergoes not three but four evaporation modes including last additional pinning mode when the contact angle decreases while the triple contact line is pinned by the nanocrystals. In contrast to previous studies, it was found out that addition of nanoparticles to aqueous surfactant solutions leads to deterioration of the spreading rate and to formation of a double co?ee ring. For all surfaces examined, superspreading in the presence and absence of quantum dot nanoparticles takes place. Despite the formation of co?ee rings on all substrates, they have di?erent morphologies. In particular, the knot-like structures are incorporated into the ring on hexamethyldisilazane- and polystyrene-coated surfaces.
关键词： Self-assembly,Superspreading,Quantum dots,Wetting dynamics,Evaporation,Nano?uids
更新于2025-09-23 15:19:57
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Growth of BaSi <sub/>2</sub> film on Ge(100) by vacuum evaporation and its photoresponse properties
摘要： We have successfully grown a polycrystalline orthorhombic BaSi2 film on a Ge(100) substrate by an evaporation method. Deposition of an amorphous Si (a-Si) film on the Ge substrate prior to BaSi2 evaporation plays a critical role in obtaining a high-quality BaSi2 film. By controlling substrate temperature and the thickness of the a-Si film, a crack-free and single-phase polycrystalline orthorhombic BaSi2 film with a long carrier lifetime of 1.5 μs was obtained on Ge substrates. The photoresponse property of the ITO/BaSi2/Ge/Al structure was clearly observed, and photoresponsivity was found to increase with increasing substrate temperature during deposition of a-Si. Furthermore, the BaSi2 film grown on Ge showed a higher photoresponsivity than that grown on Si, indicating the potential application of evaporated BaSi2 on Ge to thin-film solar cells.
关键词： photoresponse properties,Ge substrate,thin-film solar cells,BaSi2,vacuum evaporation
更新于2025-09-23 15:19:57
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Effects of non-halogenated solvent on the main properties of a solution-processed polymeric thin film for photovoltaic applications: a computational study
摘要： Organic photovoltaic (OPV) devices reached high solar conversion efficiencies but they are usually processed using halogenated toxic solvents. Hence, before OPV devices can be mass-produced by industrial processing, it would be desirable to replace those solvents with eco-friendly ones. Theoretical tools may be then a powerful ally in the search for those new solvents. In order to better understand the mechanisms behind the interaction between solvent and polymer, classical molecular dynamics (MD) calculations was used to produce a thin film of poly(4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b’]dithiophene-2,6-diyl3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl (PTB7-Th), processed using two different solvents. The PTB7-Th is widely applied as a donor material in OPVs. The first solvent is the ortho-dichlorobenzene (o-DCB), which is a highly toxic solvent widely used in lab-scale studies. The second solvent is the ortho-methylanisole (o-MA), which is an eco-friendly solvent for organic photovoltaic (OPV) manufacturing. Here we use a solvent evaporation protocol to simulate the formation of the PTB7-Th film. We demonstrate that our theoretical MD calculations were able to capture some differences in macroscopic properties of thin films formed by o-DCB or o-MA evaporation. We found that the interaction of the halogenated solvent with the polymer tends to break the bonds between the lateral thiophenediyl groups and the main chain. We show that those defects may create traps that can affect the charge transport and also can be responsible for a blue shift in the absorption spectrum. Using the Monte Carlo method, we also verified the influence of the resulting MD morphology on the mobility of holes. Our theoretical results showed a good agreement with the experimental measurements and both demonstrate that o-MA can be used to make polymer thin films without any loss of key properties for the device performance. The findings here highlights the importance of theoretical results as a guide to the morphological optimization of green processed polymeric films.
关键词： Solvent evaporation,PTB7-Th,Molecular dynamics,Organic photovoltaic,Halogenated solvents,Eco-friendly solvents,Hole mobility
更新于2025-09-23 15:19:57
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Simulation of evaporation and propulsion of small particles in a laser beam
摘要： The technique of numerical simulation of laser surface evaporation of small particles ranging in size from tens to several millimeters falling into the field of laser radiation is developed. The interaction of a laser beam with solid or liquid particles freely flying in a gas-dispersed stream is accompanied by heating and evaporation of the material, which occurs only from the irradiated part of the particle surface. The result is a reactive force created by the laser, which depends on the characteristics of the radiation and the physical properties of the particle material. The technique allows describing the pre-threshold, near-threshold and super-threshold modes of evaporation and is designed to calculate the light propulsion force due to the vapor recoil pressure arising from the irradiated part of the particle surface in the range of Mach numbers to unity. The Meshcherskii equation is used to simulate the reactive acceleration of particles. It is shown that, in the case of a pulsed laser effect, the theory is in good agreement with experimental data on reactive acceleration of aluminum, corundum, and graphite particles. A distinctive feature of the technique is the ability to calculate the gas dynamic parameters of steam and recoil pressure in a wide range of the power density of the absorbed laser radiation from 10 to 10,000 GW/m2.
关键词： laser surface evaporation,reactive force,vapor recoil pressure,small particles,Meshcherskii equation
更新于2025-09-23 15:19:57
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System for manufacturing complete Cu(In,Ga)Se2 solar cells in situ under vacuum
摘要： We present the development of a small foot-print physical vapor deposition (PVD) system for in-situ deposition of all layers required in a complete Cu(In,Ga)Se2 (CIGS) solar cell. Seven sputtering magnetrons and one valved-cracker source have been custom designed and manufactured for this system, named SpuTtering for Advanced Research (STAR). The purpose of STAR is to develop a technique to fabricate a complete CIGS solar cell, including contacts, absorber, buffer, and window layers, under high vacuum with the aim to transfer this technology to a future industrial production line. The system’s capabilities and its relatively high throughput place it somewhere in between research and industrial development levels. It is possible to work on the deposition of the back contact, the CIGS absorber, and the window layer of three solar cells simultaneously. Calibration data, selection of parameters for the deposition of the individual layers, and initial results of a complete CIGS solar cell developed with STAR are reported.
关键词： Pulsed evaporation,Thin-film photovoltaics,Cu(In,Ga)Se2,Sputtering
更新于2025-09-23 15:19:57
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Sequences of Sub-Microsecond Laser Pulses for Material Processing: Modeling of Coupled Gas Dynamics and Heat Transfer
摘要： Multipulse laser processing of materials is promising because of the additional possibilities to control the thickness of the treated and the heat-affected zones and the energy efficiency. To study the physics of mutual interaction of pulses at high repetition rate, a model is proposed where heat transfer in the target and gas-dynamics of vapor and ambient gas are coupled by the gas-dynamic boundary conditions of evaporation/condensation. Numerical calculations are accomplished for a substrate of an austenitic steel subjected to a 300 ns single pulse of CO2 laser and a sequence of the similar pulses with lower intensity and 10 μs inter-pulse separation assuring approximately the same thermal impact on the target. It is revealed that the pulses of the sequence interact due to heat accumulation in the target but they cannot interact through the gas phase. Evaporation is considerably more intensive at the single-pulse processing. The vapor is slightly ionized and absorbs the infrared laser radiation by inverse bremsstrahlung. The estimated absorption coefficient and the optical thickness of the vapor domain are considerably greater for the single-pulse regime. The absorption initiates optical breakdown and the ignition of plasma shielding the target from laser radiation. The multipulse laser processing can be applied to avoid plasma ignition.
关键词： laser evaporation,multipulse laser processing,laser plasma,heat transfer,gas dynamics
更新于2025-09-23 15:19:57
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Undoped p-type BaSi <sub/>2</sub> emitter prepared by thermal evaporation and post-annealing for crystalline silicon heterojunction solar cells
摘要： p-type BaSi2/n-type crystalline Si (p-BaSi2/n-Si) heterojunction solar cells with various BaSi2 thickness (dBaSi2) from 20 to 100 nm were fabricated using a simple preparation method, that is, post-annealing of undoped n-type BaSi2 prepared by thermal evaporation. With decreasing dBaSi2, short-circuit current density increased due to the reduction of the parasitic absorption in p-BaSi2. On the other hand, open-circuit voltage and fill factor decreased due to the increase of the leakage current. As a consequence, the solar cell with dBaSi2 = 80 nm showed a maximum conversion efficiency.
关键词： post-annealing,BaSi2,p-type emitter,heterojunction solar cells,thermal evaporation
更新于2025-09-23 15:19:57
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Development and characterization of TlGaSe2 thin film-based photodetector for visible-light photodetector applications
摘要： In current work a thermal evaporation technique has been employed to fabricate the thin films from the grown TlGaSe2 single crystal and investigated. X-ray diffraction study revealed the formation of polycrystalline films of monoclinic crystal system. The crystallite size was estimated to be 11 nm. Atomic force and scanning electron microscopy studies shows the nanocrystalline film fabrication and the size of grain was estimated. Optical study shows that the grown film is about 55% transparent in 800–1500 nm region and possess a sharp absorption edge. The direct energy gap of TlGaSe2 films was estimated around 2.31 eV. The photo current of the fabricated TlGaSe2 photodetector increases about 6 times compare to dark when exposed under 5 mW/cm2 illumination. The fabricated detector possesses high external quantum efficiency of 158% and also the detectivity reached to 5.16 ? 1010 at V ? 10 V. The on/off behaviour of the device was also studied and found that the response time for growth and decay is 88 ms and 90 ms, respectively.
关键词： A. Thin film,D. optical properties,C. X-ray diffraction,B. thermal evaporation,D. electrical properties,D. photodetector
更新于2025-09-23 15:19:57