Nature of Local Charge Carrier Motions in Porphyrin-based Bulk Heterojunction Films Revealed by Time-resolved Optical Pump-terahertz Probe Spectroscopy

Local charge carrier dynamics in diketopyrrolopyrrole (DPP)-tetrabenzoporphyrin (BP)-based bulk heterojunction (BHJ) films are investigated by optical pump-terahertz probe spectroscopy. Here we focus on the effect of the alkyl chain lengths of DPP on the carrier dynamics. In contrast to the large difference in the power conversion efficiency, similar dynamics are observed between C10-DPP-BP and C4-DPP-BP BHJ films. We discuss the origin of similarity in terms of nature of the high frequency response of photo-generated charge carriers. We studied local charge carrier dynamics of diketopyrrolopyrole (DPP)-tetrabenzoporphyrin (BP)-based bulk heterojunction (BHJ) films. Even though power conversion efficiency depends strongly on the length of alkyl chain to DPP chromophore, we found that local charge carrier mobility does not depend on it. We discuss the origin in terms of nature of the high frequency response of photo-generated charge carriers.