Radiowave Effects on an Electron–Hole Pair in a Poly(3-hexylthiophene) near Zero Magnetic Field

Abstract

To clarify the dynamics of an electron–hole (e–h) pair, which plays an important role in the performance of optoelectronic devices, the radiowave effect on photoconduction in a regioregular poly(3-hexylthiophene-2,5-diyl) film near zero magnetic field was investigated. Irradiation of the radiowaves of 1–25 MHz at zero field resulted in lower photoconduction because of a quasistatic magnetic field effect on intersystem crossing and electron spin resonance among hyperfine sublevels of the e–h pair. The recombination and dissociation rate constants of the e–h pair (107 s–1) were estimated by comparison with simulations based on the e–h pair dynamics under a perturbation treatment of the radiowave as an oscillating magnetic field using a density matrix formalism. An amplitude modulation technique of the radiowave at zero field in the frequency region <50 kHz revealed slow e–h pair formation (∼105 s–1), which is a rate-determining step for carrier recombination in the film.