Abstract
Investigations of Poly(2-methoxy-5-(2'ethyl-hexyloxy)-1,4-phenylene vinylene) (MEH-PPV)/Porous Silicon (PS) systems were carried out in order to obtain optoelectronic devices with properties of both materials. We have studied the optical and electrical characteristics of the devices made either by mixing the silicon nanocrystallites (nc-Si) with the polymer (MEH-PPV:nc-Si nanocomposite) or by depositing a polymer film on the PS layers (MEH-PPWPS nanocomposite device). For MEH-PPV/PS nanocomposite device, different concentrations of MEH-PPV and PS layers having different thickness were used for the investigation of current-voltage (I-V) characteristics. Electrical properties of the structures with relatively thin PS layer (similar to 1 mu m) significantly differ from those of thick structures. The I-V characteristics obtained on MEH-PPV:nc-Si nanocomposite showed an improvement of both the threshold voltage and current intensity as compared with those relative to MEH-PPWPS nanocomposite device. By using the Richardson-Schottky diode equation and taking into account a series resistance R-s, all the parameters of the diodes are determined and discussed. The mechanism of conduction was involved. Efficient photoluminescence (PL) from MEH-PPV:nc-Si nanocomposite is shown, due to excitation energy transfer from silicon nanocrystallites dispersed in the MEH-PPV film.