Papers by Keyword: Buffer Layer

Abstract: Organic solar cells (OSCs) have significant challenges with limited light absorption and low efficiency. This study investigates enhancing OSC performance through plasmonic effects by incorporating silver nanoparticles (AgNPs) into the hole transport layer (PEDOT:PSS). AgNP concentrations systematically varied in PEDOT:PSS (0.2%, 0.4%, 0.6%, and 0.8%) and studied their effects on device performance using UV-vis spectroscopy and current-voltage measurements. The OSC device with 0.8% AgNPs revealed a 39% increase in light absorption within the active poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) across the visible and ultraviolet spectrum, leading to a power conversion efficiency of 5.99% - twice that of the reference device. The enhanced performance is attributed to localised surface plasmon resonance effects, which improve carrier generation. These findings demonstrate a promising approach for enhancing OSC efficiency through plasmonic enhancement.

Abstract: To meet the requirements of second generation photovoltaics, spin coating and RF magnetron sputtering techniques have been utilized to fabricate zinc sulfide thin films for buffer layer optimization. During fabrication process, substrate temperatures for spin coating and RF magnetron sputtering processes are kept at room temperature and at 200 oC, respectively. Thin films are annealed at 500oC for 1 hour in an inert environment to acquire crystallinity and uniform surface morphology. XRD analysis reveals that thin films fabricated by spin coating and RF magnetron sputtering exhibit wurtzite and zinc blende crystal structures, respectively. SEM shows that the surface morphology of thin films fabricated by both techniques is uniform and homogeneous without voids and cracks. EDS results indicate that thin films fabricated via spin coating have equal stoichiometric ratio of zinc to sulfur (1:1). Whereas, an unequal stoichiometric ratio of zinc to sulfur is detected in RF magnetron sputtered thin films. According to optical studies, spin coated zinc sulfide thin films have 67% transmission with an energy band gap of 3.62 eV. While, RF magnetron sputtered thin films have 76% transmission with a wide energy band gap of 3.70 eV. Electrical properties depict that thin films fabricated by RF magnetron sputtering have higher carrier concentration, lower resistivity and higher conductivity than spin coated thin films. In comparison, RF magnetron sputtered zinc sulfide thin films exhibit best structural and optoelectronic properties for buffer layer in second generation solar cells.

Abstract: The effect of increasing Buffer Layer (BL) thickness on crystal defectivity has been investigated in 4° off-axis 4H-SiC homoepitaxy on 200mm substrates coming from different suppliers. The results, based on optical microscopy and scatter light methods, show a slight increase in morphological defects in the case of a thicker BL with respect to the standard thickness for both suppliers.

Abstract: An essential silicon carbide (SiC) manufacturing procedure for eliminating bipolar degradation in a SiC device is the detection of the basal plane dislocation (BPD) causing the phenomenon. In this work, we employed the mirror electron microscope (MEM) technique, which has higher resolution than photoluminescence. The MEM provided results for the detection of short BPDs without conversion to threading edge dislocation at the epi/sub interface. In addition, a considerable number of short BPDs were observed in the epilayer grown with the improved method, and the conversion ratio around the buffer layer could be derived.

Abstract: In laser cladding process, generation of high temperature gradients significantly impacts the output coating parameters such as mechanical and microstructural properties. Buffer layer addition between hard alloys cladding shows reduction in crack formation and also dilution rates. The present study is on Insitu temperature monitoring in laser cladding of Stellite 6 alloy with addition of buffer layer, which were compared with direct deposition of Stellite 6. The results show about 17 - 20 % low substrate temperatures with a buffer layer, indicates more uniform cooling of the hard coatings than direct cladding. The increase in laser power measures 35 - 40 % higher temperatures in both the cases due to large heat addition at the clad region. The study provides an insight into the substrate temperature evolution in cladding with and without a buffer layer.

Abstract: Herein, we report an original adaptation of an XRD set-up in order to measure the miscut angle values in our 4H-SiC on axis substrates with a high precision of ± 0.02°. This study also reveals a correlation between the formation of wide steps on 4H-SiC(0001) and the relative orientation of the SiC crystalline planes versus the gas flow direction. These two results paves the way towards the reproducible growth of graphene over wide SiC steps.

Abstract: This paper studies the characteristics of white powder generation on the buffer layer of cables under the influence of humidity and pressure. After testing, the presence of white powder in the buffer layer leads to an increase in the volume resistivity (higher than the area without white powder). The denser the white powder, the more the volume resistivity rises. The current density and surface temperature is simulated in COMSOL and observed the process of white powder generation. The volume resistivity is also measured using an electrochemical impedance spectrometer with different contents of white powder in buffer layer. The test results show that the electrochemical corrosion increase on buffer layer under high water contents in the presence of large current density. The experimental results show that when the water content of the buffer layer is 2 mL, the formation rate of white powder is the fastest; when the pressure of the buffer layer in the range of 998.2 N/m²~9982 N/m², the formation rate of white powder increases first, then decreases, and finally tends to be saturated; The main component of white powder is aluminum oxide, which is formed by chemical corrosion and electrochemical corrosion of aluminum, carbon black, sodium polyacrylate, water and etc.

Abstract: The present article reports the growth mechanism of zinc oxide (ZnO) nanowires grown on silicon substrate pre-coated with ZnO buffer layer by thermal evaporation method. ZnO nanowires are grown for different growth time of 0, 30, 90 and 120 mins with controlled supply of Ar and O₂ gas at 650 °C. The structural, morphological and crystallinity properties of ZnO nanowires are analyzed by field emission scanning electron microscopy (FESEM), energy dispersive X-ray (EDX) spectroscopy, high resolution transmission electron microscopy (HRTEM), and X-ray diffraction (XRD). FESEM images infers that, the nanowires growth is driven by self-catalysed vapor-liquid-solid mechanism, where the buffer layer serve as nucleation site. EDX spectra show the uniform composition and purity of ZnO nanowires. A strong (002) peak is detected in XRD spectra which indicates that the preferred growth orientation of the nanowires is toward the c-axis with a hexagonal wurtzite structure. The HRTEM microscopic graphs confirm the growth of nanowire along the preferred [0001] axis. Based on the analysis of grown ZnO nanowires, the probable growth mechanism is schematically presented.

Abstract: In the present study, Zn_xSn_1-xS (x = 0, 0.25, 0.5, 0.75 and 1) thin film samples were deposited by ultrasonic spray pyrolysis technique on glass substrates at 350°C to investigate the effect of variation of Zn concentration (x) on the structural, morphological, optical and electrical properties of Zn_xSn_1-xS thin films. The films were deposited by varying Zn content in the starting solution. The films deposited were found to be amorphous having root mean square (RMS) roughness ranged from 18.2 to 93.5 nm. The optical characterization by UV-Vis spectroscopy showed that the transmittance and reflectance of all samples are lower than 12.2 % and 10 % respectively. The optical band gap was estimated from the reflectance and transmittance spectra are about 3.86 eV. The carrier mobility is ranged from 113 to 2600 cm²/v.s.

Abstract: In this manuscript, the structural properties such as the distance inter-reticular of samples is studied, In the fact, four samples were used symbolized as follows: E tAg(Å), the only difference is the thickness of the Silver buffer layer (tAg= 0, 50, 100 and 150 Å) to find out how the thickness of this layer depends on the structural characteristics of the Iron thin layer, all samples are deposited using molecular beam epitaxy (MBE) at room temperature onto Si (100) substrate. The structural properties of all samples examined using X-ray diffraction method at small and high angles. The small angles X-Ray diffraction curves confirmed to us that there is a clear difference between the surface structure of the samples by varying the number of Kiessig Fringes, Also high angles X-Ray diffraction curves assured us this difference through the clear variation in the angular positions of the peaks of Bragg and the distances inter-reticular values from a sample to the other.