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We investigated the morphological and structural change in silicon nanostructures embedded in the silicon oxynitride matrix. The study has been carried out on thin films thermally annealed at high temperature, after deposition at 400°C by Electron Cyclotron Resonance Plasma Enhanced Chemical Vapour Deposition (ECRPECVD), under different deposition parameters Our study evidenced the existence of a well defined threshold for the silicon content in the film (around 47%), to get Si nano-crystallization in the silicon oxynitride matrix. Both Si nano-crystals and Si nano-columns have been observed by TEM analysis in two samples having a similar Si content but deposited under different conditions. [ABSTRACT FROM AUTHOR]

Cuprous oxide materials are of growing interest for optoelectronic devices and were produced by several chemical and physical methods. Here, we report on the structural, optical, and electrical properties of Cu x O thin films prepared by the pulsed laser deposition technique. The substrate temperature, as well as the oxygen partial pressure in the deposition chamber, were varied to monitor the copper to oxygen ratio within the deposited films. The growth conditions were carefully optimized to provide the highest conductivity and mobility. Thus, 100 nm thick cuprous oxide films (Cu 2 O) deposited at 750 °C exhibited a resistivity of 16 Ω∙cm, high mobility of 30 cm2/(V∙s), and a bandgap of around 2 eV. The film deposited at the optimized deposition parameters on Nb:STO (001) substrate with Au top electrode showed a photovoltaic response with an open circuit voltage of 0.56 V. These results path the way to efficient solar cells made with Cu 2 O films via the pulsed laser deposition technique. [Display omitted] [ABSTRACT FROM AUTHOR]

The use of photon conversion layers is an interesting way to improve the overall efficiency of solar cells. Herein we report on Nd-doped SnO 2 thin films with photon management property inserted further into CIGS based solar cells. The functionalized layers were deposited by reactive magnetron sputtering whose structural, optical and electrical properties were tuned by varying the deposition temperature. Careful analysis of the structure using XRD and XPS showed that the tetragonal rutile SnO 2 phase can be obtained at a deposition temperature as low as 100 °C. Transparency was found to be as high as 90% for all layers while the absorption edge is found to increase when increasing the deposition temperature up to 300 °C. The photoluminescence measurements under 325 nm UV laser excitation showed that 100 °C is needed for the optical activation of the rare earth. Despite the small amounts of Nd (around 0.62 at%), intense and narrow emission bands have been collected in the Near Infrared Region (NIR) which are characteristics of Nd 3+ ions whose the ionic state was confirmed by the 3d XPS core levels. Thus, the emission spectra cover a good part of the spectrum useful to the solar cell. Photoluminescence excitation spectroscopy experiments were also carried out on Nd:SnO 2 samples to get insights on the energy transfer. By exciting in the deep UV from 250 to 400 nm intense Nd emission was collected giving an experimental evidence of the down-shifting process through a resonant energy transfer from the SnO 2 host matrix to the Nd 3+ ions. Hall Effect measurements showed that the n-type character and good conductivity of the Nd doped SnO 2 films can be correlated to the highest optical activity of Nd in the matrix. An optimal condition is found for the Nd-doped SnO 2 film grown at 300 °C for which the highest PL and the best electrical data were measured. Finally, we show that the implementation of such optimized Nd–SnO 2 films on CIGS based solar cells serving as a transparent conducting oxide and a down shifting converter results in the best power conversion efficiency. [ABSTRACT FROM AUTHOR]