Out-of-Phase Electron Spin Echo Studies of Light-Induced Charge-Transfer States in P3HT/PCBM Composite

Ekaterina A Lukina; Alexander A Popov; Mikhail N Uvarov; Leonid V Kulik

doi:10.1021/acs.jpcb.5b02142

Out-of-Phase Electron Spin Echo Studies of Light-Induced Charge-Transfer States in P3HT/PCBM Composite

J Phys Chem B. 2015 Oct 29;119(43):13543-8. doi: 10.1021/acs.jpcb.5b02142. Epub 2015 Apr 22.

Authors

Ekaterina A Lukina^{1

2}, Alexander A Popov^{1

2}, Mikhail N Uvarov¹, Leonid V Kulik^{1

2}

Affiliations

¹ Voevodsky Institute of Chemical Kinetics and Combustion of the Siberian Branch of the Russian Academy of Sciences , Institutskaya 3, Novosibirsk 630090, Russia.
² Novosibirsk State University , Pirogova 2, Novosibirsk 630090, Russia.

PMID: 25867974
DOI: 10.1021/acs.jpcb.5b02142

Abstract

The light-induced charge-transfer (CT) state in the composite of the conductive polymer poly(3-hexylthiophene) (P3HT) and the fullerene derivative [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) has been studied by electron spin echo (ESE) spectroscopy. The out-of-phase ESE signal corresponding to the spin-correlated radical pair P3HT(+)/PCBM(-) has been observed in this composite material. The time-domain ESE shape for different delays between the laser flash and the microwave pulse sequence has been analyzed. In order to explain the evolution of the out-of-phase ESE signal as a function of the delay between the microwave pulses, a model of the CT state is proposed. The hole is assumed to be delocalized on the P3HT chain over several thiophene subunits, while the point-dipole approximation is used to describe the interaction with the electron on PCBM. The distribution of distances between the positive and negative charges in the CT state has been evaluated.