Photoinduced electron transfer reactions in mixed films of pi-conjugated polymers and a homologous series of tetracyano-p-quinodimethane derivatives

Near-steady-state photoinduced absorption (PIA) and photoluminescence studies are presented on photoinduced electron transfer reactions from poly[2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylene vinylene] (MEH-PPV) and poly[3-(2-(3-methylbutoxy)ethyl)thiophene] (P3MBET) as donors (D) onto a homologous series of tetracyano-p-quinodimethane (TCNQ) derivatives containing fused aromatic rings as acceptors (A) to systematically study the effect of acceptor electron affinity. We observe that composite films of these D/A couples give rise to long-lived charge separated states upon photoexcitation, as evidenced from the formation of polaron bands (radical cation absorption) in the PIA and the concomitant loss of the metastable triplet PIA and photoluminescence that are observed in pristine MEH-PPV and P3MBET. We find that the efficiency of the photoinduced electron transfer reaction correlates with the reduction potential of the acceptors.