Exciton dissociation and migration in enhanced-order conjugated polymer/nanoparticle hybrid materials

The mechanisms of exciton dissociation and migration in the conjugated polymer (poly(2-methoxy-5-(2'-ethyl)(hexyloxy)1,4-phenylenevinylene)(MEH-PPV) / CdSe nanoparticle hybrid materials were investigated by steady-state and time-resolved photoluminescence spectroscopy. Rapid exciton dissociation at the nanoparticle/polymer interfaces leading to quenching of the photoluminescence efficiency η and shortening of the measured lifetime τPL is observed. The excitons which contribute to the remaining luminescence in polymer will migrate to the lower energy sites with longer conjugated sequences in the composites. The result is evident from the observations of a redshift of the photoluminescence peak positions, a progressive decrease of the Huang-Rhys factor S and an increase in the nature radiative lifetime τR with increasing CdSe nanoparticle content. The solar cell based on the MEH-PPV / CdSe nanoparticle hybrid materials are fabricated and the transport mechanism of the device will also be discussed.