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Abstract: In this paper, epitaxial silicon films were grown on annealed double layer porous silicon by LPCVD. The evolvement of the double layer porous silicon before and after thermal annealing was investigated by scanning electron microscope. X-ray diffraction and Raman spectroscopy were used to investigate the structural properties of the epitaxial silicon thin films grown at different temperature and different pressure. The results show that the surface of the low-porosity layer becomes smooth and there are just few silicon-bridges connecting the porous layer and the substrate wafer. The qualities of the epitaxial silicon thin films become better along with increasing deposition temperature. All of the Raman peaks of silicon films with different deposition pressure are situated at 521cm−1 under the deposition temperature of 1100°C, and the Raman intensity of the silicon film deposited at 100Pa is much closer to that of the monocrystalline silicon wafer. The epitaxial silicon films are all (400)-oriented and (400) peak of silicon film deposited at 100Pa is more symmetric. [Copyright &y& Elsevier]

Abstract: The electronic band structure and elastic constants of SnS2 and SnSe2 have been calculated by using density-functional theory (DFT). The calculated band structures show that SnS2 and SnSe2 are both indirect band gap semiconductors. The upper valence bands originate mainly from Sp and Snd electrons, while the lowest conduction bands are mainly from (S, Se) p and Sns states. The calculated elastic constants indicate that the bonding strength along the [100] and [010] direction is stronger than that along the [001] direction and the shear elastic properties of the (010) plane are anisotropic for SnS2 and SnSe2. Both compounds exhibit brittle behavior due to their low B/G ratio. Relationships among volumes, the heat capacity, thermal expansion coefficients, entropy, vibrational energy, internal energy, Gibbs energy and temperature at various pressures are also calculated by using the Debye mode in this work. [Copyright &y& Elsevier]

Abstract: The lattice constants and elastic constants of the kesterite-type Cu2ZnSnS4 have been calculated using density-functional theory (DFT). The calculated lattice constants are in good agreement with the experimental data. The calculated elastic constants indicate that the bonding strength along the [100] and [010] directions is as strong as the one along the [001] direction. The high B/G ratio shows that the kesterite-type Cu2ZnSnS4 compound has ductile behavior. Finally, using the Debye model, the volume, bulk modulus and heat capacity as a function of temperature for the kesterite-type CZTS have been estimated at different pressures. The Debye temperature and Gruneisen parameter are 157K and 2.28 at 300K temperature, respectively. The present results can give some information for the design of the kesterite-type CZTS compounds, and these can also be used to stimulate future experimental and theoretical work. [Copyright &y& Elsevier]

Abstract: To explore the origin of low conversion efficiency for novel β-FeSi2/c-Si heterojunction solar cells, the effect of surface recombination and interface states on the cell performance has been investigated by numerical simulation. The present results show that surface recombination of β-FeSi2 film plays an important role in limiting the cell property since the photovoltaic behavior of β-FeSi2 is quite sensitive to surface recombination due to its especial characteristic of very high optical absorption coefficient. Surface quality of β-FeSi2 film should be much improved for better cell performance. In addition, it is shown that interface states between β-FeSi2 film and crystalline silicon are critical to device characterization. Interface states should be minimized to obtain higher conversion efficiency. If surface recombination and interface states can be best suppressed, potential conversion efficiency for the cell may be up to 28.12% at 300K under illumination of AM 1.5, 100mW/cm2. [Copyright &y& Elsevier]

Abstract: In this paper, numerical simulations on the performance of p-type β-FeSi2 emitter/n-type crystalline Si base heterojunction solar cells are carried out using PC1D software. The dependences of performance on layer thickness and doping concentration in the emitter region are analyzed. The influences of main recombination mechanisms in the emitter region for cell characterization are discussed. The simulation results show that both emitter thickness and doping concentration have very important influences on the property of β-FeSi2/c-Si heterojunction solar cells. These two parameters need to be jointly selected to improve cell performance. The optimal values of emitter thickness and doping concentration are 350nm and 2×1017 cm−3 for the cell structure, respectively. Moreover, cell efficiency can be enhanced by suppressing carrier recombination rate. Bulk and surface recombinations must be minimized by improving the material growth and surface passivation process, and the Auger and radiative recombination can be suppressed by reducing carrier concentrations appropriately. With the emitter parameter optimized, device performance can be well improved. [ABSTRACT FROM AUTHOR]

Abstract: Epitaxial silicon thin film on textured double layer porous silicon (DLPS) was demonstrated. The textured DLPS was formed by electrochemical etching using two different current densities on the silicon wafer that are randomly textured with upright pyramids. Silicon thin films were then grown on the annealed DLPS, using low-pressure chemical vapor deposition (LPCVD). The reflectance of the DLPS and the grown silicon thin films were studied by a spectrophotometer. The crystallinity and topography of the grown silicon thin films were studied by Raman spectroscopy and SEM. The reflectance results show that the reflectance of the silicon wafer decreases from 24.7% to 11.7% after texturing, and after the deposition of silicon thin film the surface reflectance is about 13.8%. SEM images show that the epitaxial silicon film on textured DLPS exhibits random pyramids. The Raman spectrum peaks near 521cm−1 have a width of 7.8cm−1, which reveals the high crystalline quality of the silicon epitaxy. [ABSTRACT FROM AUTHOR]

Abstract: Aluminum doped zinc oxide (AZO) films were deposited by radio frequency (RF) magnetron sputtering on the Al2O3-coated and bare soda lime glass substrates, respectively. The properties of AZO films were analyzed using X-ray diffraction (XRD), atomic force microscope (AFM), Hall effect measurement and ultraviolet–visible (UV–vis) spectrophotometer. The results of XRD measurement showed that all the AZO thin films had a preferentially oriented (002) peak and the intensity of (002) peak decreased with increase in the thickness of the Al2O3 buffer layer. The Hall measurement results showed that the conductivity of the AZO film with a 3nm Al2O3 buffer layer had a remarkable 41.3% increase when compared with that of the single AZO film. The figures of merit from optical transmittance and electrical conductivity for AZO films on the 3nm Al2O3-coated and bare glass substrates were 5466 and 3772Scm−1, respectively. All the results suggested that the use of an ultrathin Al2O3 buffer layer effectively improved the quality of AZO film on the glass substrate. [Copyright &y& Elsevier]