A Comparative Study of the Effect of Metallic Au and ReO3 Nanoparticles on the Performance of Silicon Solar Cells

The influence of gold (similar to 35 nm diameter) as well as ReO3 (similar to 17 nm diameter) nanoparticles placed atop silicon photovoltaic devices on absorption and photocurrent generation has been investigated. The nanoparticles improve the power transmission into the semiconductor and consequently, the photocurrent response at wavelengths corresponding to plasmon absorption. An increase in short circuit current up to 4.5% under simulated solar irradiation was observed with the ReO3 nanoparticles, while the gold nanoparticles showed enhancements up to 6.5%. The increase in photocurrent is observed at wavelengths corresponding to the maxima in the surface plasmon resonance absorption spectra. (C) 2010 The Japan Society of Applied Physic

Tuning the emission bands of nanophosphors through the refractive index of the medium

Photoluminescence spectra of nanophosphors including the yellow phosphor YAG:Ce as well as the green and red phosphors based on CdSe nanoparticles have been studied in the media of oxide gels and polymers of different refractive indices. The oxide gels employed are of silica, zirconia and their solid solutions with the refractive index, n, varying between 1.46 and 2. Different polymers afforded the variation of refractive index in the range 1.35-1.58. The wavelength corresponding to emission maxima of the phosphors are found to shift to lower wavelengths with increase in the refractive index of the medium. The shifts in the various media are found to be proportional to the refractive index term, n2−½n2+1. The sensitivity of the emission maxima of the nanophosphors to the medium refractive index may be useful for practical applications such as solid-state lighting

Photoluminescence and photoconducting properties of ZnO nanoparticles

Photoluminescence and photoconducting properties of thinfilms of colloidal ZnO nanoparticles have been investigated by annealing them in an oxygen atmosphere at different temperatures. The changes in the defect-related emission and the photoconducting properties with the annealing temperature have been examined in detail

A Raman study of multiferroic LuMnO3

Magnetic and dielectric measurements confirm the multiferroic nature of LuMnO3. Raman spectra of LuMnO3 have been recorded in the 77-800 K range covering both the antiferromagnetic transition at 90 K and the ferroelectric-paraelectric transition at 750 K. The changes in the phonon modes frequencies and band-widths indicate the presence of phonon-spin coupling in the antiferromagnetically ordered phase. The ferroelectric-paraelectric transition is accompanied by the broadening and disappearance of many of the phonon modes. Some of the phonon modes also show anomalies at the ferroelectric transition

Enhanced photoelectrochemical response of 1D TiO2 by atmospheric pressure plasma surface modification

In this paper we demonstrate the use of atmospheric pressure plasma jet (APPJ) to functionalize the surface of hydrothermally synthesized vertically aligned TiO2 nanorods (TNRs) for photo electrochemical (PEC) application. The TNRs functionalized with the atmospheric pressure He-plasma showed relatively higher crystallinity, improved light absorption, and change in the morphology with additional surface area, leading to an enhanced photocurrent density than that of the untreated. Achieving the PEC performance on par with the best in the literature, this APPJ treatment is shown to be a promising technique to obtain better functionality with TNR kind of materials and many other nano-micro systems for various applications such as PEC hydrogen generation

White-light sources based on composites of GaN nanocrystals with conducting polymers and nanophosphors

Optical properties of nanocomposites of GaN nanocrystals, 2–4 nm in diameter, with conjugated polymers such as poly(2-methoxy,5-(2-ethylhexoxy)-1,4-phenylenevinylene (MEHPPV) as well as with phosphors nanoparticles have been investigated for use as white light sources. Photoluminescence spectra of the nanocomposites with different weight ratios of the two components are reported. Weak electroluminescence has been observed in the case of MEHPPV-GaN nanocomposites. The GaN–nanophosphor composites exhibit a high quality white light with good CIE coordinates along with an excellent colour rendering index

A Raman study of multiferroic LuMnO<SUB>3</SUB>

Magnetic and dielectric measurements confirm the multiferroic nature of LuMnO<SUB>3</SUB>. Raman spectra of LuMnO<SUB>3</SUB> have been recorded in the 77-800 K range covering both the antiferromagnetic transition at 90 K and the ferroelectric-paraelectric transition at 750 K. The changes in the phonon modes frequencies and band-widths indicate the presence of phonon-spin coupling in the antiferromagnetically ordered phase. The ferroelectric-paraelectric transition is accompanied by the broadening and disappearance of many of the phonon modes. Some of the phonon modes also show anomalies at the ferroelectric transition

White-light sources based on composites of GaN nanocrystals with conducting polymers and nanophosphors

Optical properties of nanocomposites of GaN nanocrystals, 2–4 nm in diameter, with conjugated polymers such as poly(2-methoxy,5-(2-ethylhexoxy)-1,4-phenylenevinylene (MEHPPV) as well as with phosphors nanoparticles have been investigated for use as white light sources. Photoluminescence spectra of the nanocomposites with different weight ratios of the two components are reported. Weak electroluminescence has been observed in the case of MEHPPV-GaN nanocomposites. The GaN–nanophosphor composites exhibit a high quality white light with good CIE coordinates along with an excellent colour rendering index

Enhancing photo-induced ultrafast charge transfer across heterojunctions of CdS and laser-sintered TiO2 nanocrystals

Enhancing the charge transfer process in nanocrystal sensitized solar cells is vital for the improvement of their performance. In this work we show a means of increasing photo-induced ultrafast charge transfer in successive ionic layer adsorption and reaction (SILAR) CdS-TiO2 nanocrystal heterojunctions using pulsed laser sintering of TiO2 nanocrystals. The enhanced charge transfer was attributed to both morphological and phase transformations. At sufficiently high laser fluences, volumetrically larger porous networks of the metal oxide were obtained, thus increasing the density of electron accepting states. Laser sintering also resulted in varying degrees of anatase to rutile phase transformation of the TiO2, producing thermodynamically more favorable conditions for charge transfer by increasing the change in free energy between the CdS donor and TiO2 acceptor states. Finally, we report aspects of apparent hot electron transfer as a result of the SILAR process which allows CdS to be directly adsorbed to the TiO2 surface