Photogeneration of charge carriers in blends of conjugated polymers and semiconducting nanoparticles

Abstract

Composites of nanoparticles and conjugated polymers are studied via photoluminescence (PL), photoinduced absorption spectroscopy and light induced electron spin resonance (LESR) spectroscopy. Two different types of nanoparticles were investigated namely cadmium selenide and indium phosphide. They were available with a tri- n-octylphosphine-oxide–tri- n-octylphosphine shell or pyridine washed. Nanoparticles were mixed with poly(2-methoxy-5-(3-,7-dimethyloctyloxy)-1,4-phenylenevinylene) (OC 1C 10-PPV) in different weight ratios. The quenching of the PL, the formation of polaronic radicals as well as the occurrence of two new absorption bands are explained in the frame of a photoinduced charge transfer between the polymer and the nanocrystal. For a detailed analysis, the lifetime and recombination kinetics are studied by varying the chopper frequency and by changing the laser power. We find a broad distribution of lifetimes, which suggests a dispersive recombination process. With LESR the charge transfer process is confirmed and the g-factor of the polymer cation was determined. Time dependent studies show the involving of long living species in the recombination process.