Electrogenerated chemiluminescence and interfacial charge transfer dynamics of poly(3-hexylthiophene-2,5-diyl) (P3HT)–TiO2nanoparticle thin film

Abstract

We present electrogenerated chemiluminescence (ECL) and photoluminescence (PL) characteristics of poly(3-hexylthiophene-2,5-diyl) (P3HT) thin films incorporated with monodisperse TiO₂ nanoparticles prepared using a hydrothermal reaction in the presence of oleylamine and oleic acid. The ECL turn-on potential decreases in the presence of TiO₂ nanocrystals, accompanied with an increase in ECL intensity. Only a minor ECL quantum efficiency decrease is obtained in the presence of <40 wt% TiO₂, indicating the formation of an effective interpenetrating network of TiO₂ and disordering of polymer packing to allow the ECL coreactant to transport through the film for efficient electroluminescence. In contrast, PL quenching increases with the weight percentage of TiO₂ and significant PL quenching is obtained when the P3HT film contains up to 80 wt% TiO₂ due to charge transfer. Polaron absorption after the photoinduced charge separation in the presence of 80 wt% TiO₂ nanoparticles is significantly enhanced with longer-lived lifetimes of >1000 ps in contrast to the neat P3HT film. The absorption of polarons created at the P3HT–TiO₂ interface is found to increase with the P3HT–TiO₂ interfacial area per unit volume.