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Deposition of gold nanoparticles upon bare and indium tin oxide film coated glass based on annealing process
摘要： We presented a simple and efficient strategy for deposition of gold nanoparticles (AuNPs) upon transparent bare and indium tin oxide (ITO) film coated glass substrate using gold colloids as Au sources. The method involved two steps: embedding in polyvinyl alcohol (PVA) film and annealing at high temperature. The AuNPs deposited on solid substrate because of migration and coalescence of gold at high temperature. The optical and structural properties of the AuNPs were characterised by UV-vis absorption spectra and scanning electron microscopy. The results indicate that the surface of AuNPs upon substrate was clean as annealing at 600 °C for 0.5 h. The size of AuNPs deposited on ITO glass increased with annealing time and volume of PVA-AuNPs. Meanwhile, the localised surface plasmon resonance peak of AuNPs deposited on substrate was also gradual red-shift. In addition, the size of AuNPs deposited on ITO substrate was larger than that on bare glass. This work provides a simple, low-cost and large-scale method for fabrication of substrate-based AuNPs, which is benefit for exploiting biosensors, photonic devices and optoelectronic devices.
关键词： thermal annealing,solid substrate,Gold nanoparticles,indium tin oxide film coated glass
更新于2025-11-19 16:56:35
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Polycrystal Synthesis, Crystal Growth, Structure, and Optical Properties of AgGaGe <sub/><i> <i>n</i> </i> </sub> S <sub/> 2( <i> <i>n</i> </i> +1) </sub> ( <i>n</i> = 2, 3, 4, and 5) Single Crystals for Mid-IR Laser Applications
摘要： AgGaGenS2(n+1) crystal is a series of quaternary for mid-IR laser applications of nonlinear optical materials converting a 1.064 μm pump signal (Nd:YAG laser) to 4?11 μm laser output, but only AgGaGeS4 has attracted the most attention, remaining the other promising AgGaGenS2(n+1) crystal whose physicochemical properties can be modulated by n value. In this work, AgGaGenS2(n+1) (n = 2, 3, 4, and 5) polycrystals are synthesized by vapor transport and mechanical oscillation method with di?erent cooling processes. High-resolution X-ray di?raction analysis and re?nement have revealed that all the four compounds are crystallized in the noncentrosymmetric orthorhombic space group Fdd2, resulting in the excellent nonlinear optical property, and the distortion of tetrahedron with the variation of n value causes the discrepancy of physicochemical property. Besides, using the modi?ed Bridgman method, AgGaGenS2(n+1) single crystals with 15 mm diameter and 20?40 mm length have been grown. We have discussed the structure and composition of AgGaGenS2(n+1) by XPS spectra and analyzed the three kinds of vibration modes of tetrahedral clusters by the Raman spectra. The Hall measurement indicates that the AgGaGenS2(n+1) single crystals are p-type semiconductor, and the carrier concentration decreases with the increasing n value. All the transmittances of as-grown AgGaGenS2(n+1) samples exceeds 60% in the transparent range, especially the transmittance of AgGaGe2S6, is up to 70% at 1064 nm, and the band gap of as-grown crystal increases from 2.85 eV for AgGaGe2S6 to 2.92 eV for AgGaGe5S12. After a thermal annealing treatment, the absorptions at 2.9, 4, and 10 μm have been eliminated, and the band gap changed into the range of 2.89?2.96 eV.
关键词： Hall measurement,nonlinear optical materials,thermal annealing treatment,vapor transport,AgGaGenS2(n+1),Bridgman method,Raman spectra,mid-IR laser applications,XPS spectra,mechanical oscillation method
更新于2025-11-14 15:27:09
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Effects of fluorination and thermal annealing on charge recombination processes in polymer bulk-heterojunction solar cells
摘要： We investigate the effect of fluorination on the photovoltaic properties of an alternating conjugated polymer composed of 4,8-di-2-thienylbenzo[1,2-b:4,5-b0]dithiophene and 4,7-bis([2,20-bithiophen]-5-yl)-benzo-2-1-3-thiadiazole (4TBT) units in bulk-heterojunction solar cells. The unsubstituted and fluorinated polymers afford very similar open-circuit voltages and fill factor values, but the fluorinated polymer performed better due to enhanced aggregation which provides a higher photocurrent. The photovoltaic performance of both materials improved upon thermal annealing at 150–200 °C as a result of a significantly increased fill factor and open-circuit voltage, counteracted by a slight loss in photocurrent. Detailed studies of the morphology, light intensity dependence, external quantum efficiency and electroluminescence allowed the exploration of the effects of fluorination and thermal annealing on the charge recombination and the nature of the donor–acceptor interfacial charge transfer states in these films.
关键词： polymer bulk-heterojunction solar cells,thermal annealing,charge recombination,fluorination,photovoltaic properties
更新于2025-10-22 19:40:53
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In situ Characterization of Phase Transition of Amorphous Poly(9,9-di-n-octyl-2,7-fluorene) Thin Film During Thermal Annealing
摘要： Amorphous poly(9,9-di-n-octyl-2,7-fluorene)(PFO) thin films were characterized in situ via thermal annealing based on grazing incidence X-ray diffraction(GIXRD) profiles, UV-visible absorption spectrophotometry, and Fourier transform infrared spectroscopy(FTIR). The results of GIXRD indicated that the amorphous phase transformed into a crystalline phase when the annealing temperature was higher than 80 °C. Different outcomes were elicited for the intensities and d-spacings of the diffraction peaks below and above 80 °C, which were attributed to the formation of the κ-phase. The mechanism of phase transition was revealed by in situ UV-visible absorption and FTIR spectra, whereby the rearrangement of the side chains was dominant and the movement of the main chains was minimal, even when the annealing temperature was lower than 80 °C. In contrast, the rearrangement of the main chains was dominant when the temperature was higher than 80 °C.
关键词： Liquid crystalline κ-phase,Thermal annealing,Phase transition,Polyfluorene
更新于2025-09-23 15:23:52
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Investigation on annealing temperature-dependent optical properties of electron beam evaporated ZnSe thin films
摘要： This research work is devoted to studying optical properties of zinc selenide (ZnSe) thin films deposited by electron beam evaporation technique and annealed at different temperatures in a nitrogen environment. The structural analysis by X-ray diffraction confirmed that the obtained ZnSe films had cubic zinc-blende structure with preferred orientation along plane (111). Based on Swanepoel's envelope method, some important optical parameters such as absorption coefficient, extinction coefficient, refractive index and optical band gap, were evaluated through the transmission spectrum ranging from 300 to 1500 nm at room temperature. The optical band gap increased from 2.52 to 2.65 eV with the increasing annealing temperature. However, both the thickness and refractive index of the films decreased. In addition, the dispersion parameters of the refractive index and energy were also studied by using Wemple-DiDomenico single oscillator model.
关键词： Optical properties,Thin films,Electron beam evaporation,Zinc selenide,Thermal annealing
更新于2025-09-23 15:21:21
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Structural and electrical properties of Pd/p-GaN contacts for GaN-based laser diodes
摘要： In this paper, the properties of Pd-based p-contacts on GaN-based laser diodes are discussed. Pd is often the metal of choice for ohmic contacts on p-GaN. However, for Pd/p-GaN ohmic contacts, nanovoids observed at the metal/semiconductor interface can have a negative impact on reliability and also reproducibility. The authors present a thorough analysis of the microstructure of the Pd/p-GaN interface by x-ray photoelectron spectroscopy (XPS) and scanning transmission electron microscopy (STEM). STEM data show that the microvoids at the p-GaN/Pd interface form during rapid thermal annealing. A combination of the following effects is suggested to support the void formation: (1) the differences in thermal expansion coefficients of the materials; (2) excess matrix or impurity atoms in the semiconductor, at the interface, and in the metals, which are released as gases; and (3) the strong antisurfactant effect of Pd on Ga-rich p-GaN surfaces. A slow temperature ramp during contact annealing reduces the formation of voids likely by suppressing the accumulation of gases at the interface. XPS data show that the Ga/N ratio can be reduced by suitable cleaning of the p-GaN surface, which enhances Pd adhesion. As a result, the quality of the contact system is improved by the systematic optimization of the surface cleanliness as well as the annealing parameters, leading to void-free and clean Pd/p-GaN interfaces. The specific contact resistance, extracted from linear transmission line method measurements, is reduced by an order of magnitude to 2 × 10?3 Ω cm2 at 1 mA for the same epitaxial layer stack.
关键词： Pd/p-GaN contacts,STEM,nanovoids,ohmic contacts,rapid thermal annealing,XPS,GaN-based laser diodes
更新于2025-09-23 15:21:01
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Silicon nanocrystal hybrid photovoltaic devices for indoor light energy harvesting
摘要： Silicon nanocrystals (SiNCs) featuring size-dependent novel optical and electrical properties have been widely employed for various functional devices. We have demonstrated SiNC-based hybrid photovoltaics (SiNC-HPVs) and proposed several approaches for performance promotion. Recently, owing to the superiorities such as low power operation, high portability, and designability, organic photovoltaics (OPVs) have been extensively studied for their potential indoor applications as power sources. SiNCs exhibit strong light absorption below 450 nm, which is capable of sufficient photocurrent generation under UV irradiation. Therefore, SiNC-HPVs are expected to be preferably used for energy harvesting systems in indoor applications because an indoor light source consists of a shorter wavelength component below 500 nm than solar light. We successfully demonstrated SiNC-HPVs with a PCE as high as 9.7%, corresponding to the output power density of 34.0 mW cm?2 under standard indoor light irradiation (1000 lx). In addition, we have found that SiNC defects working as electron traps influence the electrical properties of SiNCs substantially, a thermal annealing process was conducted towards the suppression of defects and the improvement of the SiNC-HPVs performance.
关键词： Silicon nanocrystals,Power conversion efficiency,Indoor light energy harvesting,Thermal annealing,Hybrid photovoltaics
更新于2025-09-23 15:21:01
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Highly Efficient All-Small-Molecule Organic Solar Cells with Appropriate Active Layer Morphology by Side Chain Engineering of Donor Molecules and Thermal Annealing
摘要： It is very important to fine-tune the nanoscale morphology of donor:acceptor blend active layers for improving the photovoltaic performance of all-small-molecule organic solar cells (SM-OSCs). In this work, two new small molecule donor materials are synthesized with different substituents on their thiophene conjugated side chains, including SM1-S with alkylthio and SM1-F with fluorine and alkyl substituents, and the previously reported donor molecule SM1 with an alkyl substituent, for investigating the effect of different conjugated side chains on the molecular aggregation and the photophysical, and photovoltaic properties of the donor molecules. As a result, an SM1-F-based SM-OSC with Y6 as the acceptor, and with thermal annealing (TA) at 120 °C for 10 min, demonstrates the highest power conversion efficiency value of 14.07%, which is one of the best values for SM-OSCs reported so far. Besides, these results also reveal that different side chains of the small molecules can distinctly influence the crystallinity characteristics and aggregation features, and TA treatment can effectively fine-tune the phase separation to form suitable donor–acceptor interpenetrating networks, which is beneficial for exciton dissociation and charge transportation, leading to highly efficient photovoltaic performance.
关键词： small molecule donor materials,all-small-molecule organic solar cells,interpenetrating networks,side-chain engineering,thermal annealing
更新于2025-09-23 15:21:01
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A Thermally Induced Perovskite Crystal Control Strategy for Efficient and Photostable Widea??Bandgap Perovskite Solar Cells
摘要： Wide-bandgap perovskite solar cells (WBG PSCs) have gained attention as promising tandem partners for silicon solar cells due to their complementary absorption, superb open-circuit voltage, and easy solution process. Recently, both their performance and stability have been improved by compositional-engineering or defect-passivation strategies, due to modulation of perovskite crystal size and reduction of crystal defects. In this work, we report a thermally induced phase control (TIPC) strategy, which enables efficient and photostable WBG PSCs without any compositional engineering by exploring a thermal annealing process window of WBG perovskite films for the annealing temperature and time range of 100-175°C and 3-60 minutes, respectively. Within this window, we found a key annealing regime that produces preferred crystal orientations of lead iodide and the WBG perovskite, suppressing phase segregation and reducing charge recombination in the perovskites. The WBG PSC (composition of FA0.75MA0.15Cs0.1PbI2Br and Eg of 1.73 eV) optimized by TIPC exhibited an excellent power conversion efficiency (PCE) of 18.60% and improved operational stability, maintaining >90% of the maximum PCE (during maximum power point tracking) without encapsulation after 12-hour operation under AM 1.5G irradiation in ambient air conditions and after 500-hour operation under white LED irradiation (100 mW cm-2) in inert N2 gas conditions.
关键词： wide-band gap perovskite,thermal annealing process,operational stability,perovskite solar cells,invariant bandgap
更新于2025-09-23 15:21:01
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Distinctive features of diffusion-controlled radiation defect recombination in stoichiometric magnesium aluminate spinel single crystals and transparent polycrystalline ceramics
摘要： MgAl2O4 spinel is important optical material for harsh radiation environment and other important applications. the kinetics of thermal annealing of the basic electron (F, F+) and hole (V) centers in stoichiometric MgAl2O4 spinel irradiated by fast neutrons and protons is analyzed in terms of diffusion-controlled bimolecular reactions. properties of MgAl2O4 single crystals and optical polycrystalline ceramics are compared. it is demonstrated that both transparent ceramics and single crystals, as well as different types of irradiation show qualitatively similar kinetics, but the effective migration energy Ea and pre-exponent D0 are strongly correlated. Such correlation is discussed in terms of the so-called Meyer-Neldel rule known in chemical kinetics of condensed matter. The results for the irradiated spinel are compared with those for sapphire, MgO and other radiation-resistant materials.
关键词： diffusion-controlled bimolecular reactions,MgAl2O4 spinel,thermal annealing,Meyer-Neldel rule,radiation defect recombination
更新于2025-09-23 15:21:01