LAUSR

Abstract The influence of the 1,2-benzopyrone (BP) and 2,5-diphenyloxazole (PPO, DPO) additives on the formation, separation, motion and recombination of charge carriers in the poly(3-dodecylthiophene):[6,6]-phenyl-C61-butanoic acid methyl ester (P3DDT:PC61BM) organic photovoltaics was investigated by the light-induced electron paramagnetic resonance (LEPR) and NIR-Vis-UV spectroscopy within the wide temperature and photon energy range. These processes were interpreted in the framework of the exchange interaction of spin ensembles differently distributed in bulk heterojunctions of the P3DDT:PC61BM composite. The concentration, composition and dynamics of spin charge carriers were shown to be determined by the modification degree of the sample with small molecules, the energy of the light photons as well as the number, spatial distribution and energetic depth of spin traps formed in the disordered polymer matrix. Electronic functionality of the composite becomes better after its doping with BP and PPO additives up to optimal weight levels of 0.03 and 0.06, respectively. Such modification can improve the morphology/ordering of the composite that increases the number of highly mobile charge carriers due to the release of a part of carriers captured by energetically deep spin traps. This increases an exchange interaction between spin ensembles, reduces the number and depth of electron spin traps that, in turn, prevents the recombination of charge carriers and accelerates the power conversion.