Preparation Of Nanocrystal Silicon/polymer Composites And Study On Their Opto-electronic Properties

Colloidal silicon nanocrystals have been prepared by the technique of pulsed laser ablation and radio frequency (rf) plasma discharge, respectively. The silicon/MEH-PPV composites have been synthesized by spin coating. Fourier transform infrared spectroscopy (FTIR), Raman scattering, atomic force microscopy(AFM), scan electron microscopy (SEM) and ultraviolet-visible (UV-VIS) transmission spectra are used to analyze the microstructure characteristics and optical absorption properties of the films. The luminescence mechanism and the dynamic processes are discussed in detail by photoluminescence (PL) spectra, photoluminescence excitation (PLE) spectra, PL intensity decay spectra.The influence of the laser fluence on PL of the samples prepared by pulsed laser ablation was investigated. The result shows that the Si-ncs are partially oxidized during synthesis and with the increase of laser fluence, a considerable increase of PL intensity and a slight blueshift of PL maximum were observed. The alterable PL is essentially due to the quantum confinement effect, the emission at 2.2 eV and 3.1 eV are attributed to the Eδcenters and a H-complexed O vacancy situated at the Si crystallite/oxide interface, respectively.The influence of the gas flux on microstructure and optical properties of the samples prepared by the rf plasma discharge was investigated. The result indicates that the optical gap of the samples decreases and the PL band redshits with the gas flux decreases. The further study suggests that the particle residence time and the crystalline time in the plasma zone increase with the the gas flux decreases, and then a large amount of Si atoms aggregate and a larger particle is then formed.The study of the silicon/MEH-PPV composites shows that the adulterate of the silicon improves the short wavelengh absorption of the MEH-PPV. With increase of the silicon content, the PL intensity and the PL life of the MEH-PPV decrease while the PL life of the silicon increases. The area of the interface between silicon and MEH-PPV increases with the content of the silicon increases, so that the efficiency of the energy transfer from MEH-PPV to silicon increased. The study of photovoltaic of the composite device suggests that the short-circuit current and the power-conversion efficiency increase with the adulteration of silicon.