Carrier Generation Process in Poly(p-phenylene vinylene) by Fluorescent Quenching and Delayed-Collection-Field Techniques

The carrier generation process in poly( p -phenylene vinylene) (PPV) has been investigated by using field-induced fluorescent quenching and delayed-collection-field techniques under pulsed illumination. Relative photoresponse and fluorescent quenching have been measured at electric fields of up to 300 V/μm. The results demonstrate a linear relation between fluorescent quenching and photoresponse at high electric fields, indicating that almost all field-quenched excited states lead to carrier generation. Experimental results also indicate that the time decay of e−h pairs is highly dispersive and the majority (70%) of them decay nonexponentially to ground state in ∼1 ms after illumination. Fluorescent quenching and carrier generation efficiencies obtained at the highest applied electric field are 34% and 42%, respectively. Results also suggest that carrier generation in PPV is a two-step process. In the first step, excited singlet states dissociate into bound geminate e−h pairs, and in the second step, the geminate pairs are separated into free carriers. Both steps are influenced by the applied electric field.