Quadrimolecular recombination kinetics of photogenerated charge carriers in regioregular poly(3-alkylthiophene)/fullerene composites

Abstract

The recombination kinetics of photogenerated charge carriers in composites of regioregular poly(3-alkylthiophene)s and C60 have been investigated by a transient response of light-induced electron spin resonance (LESR). The dependence of the prompt decay component on excitation-light intensity Iex shows that quadrimolecular recombination (QR) is dominant at higher Iex while bimolecular recombination is relatively important at lower Iex. The time decay of the LESR intensity is also well explained by the QR model. The temperature dependence of the QR rate constant clearly shows a crossover from hopping to tunneling behavior with decrease of temperature; the activation energy for the hopping of 0.10 eV is obtained.