Electrogenerated chemiluminescence and interfacial charge transfer dynamics of poly(3-hexylthiophene-2,5-diyl) (P3HT)-TiO2 nanoparticle thin film

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.