Acceptor Energy Offset Manages Ultrafast Recombination Dynamics in Donor-Acceptor Mixtures

V G Pavelyev,T V Orekhova,D Yu Paraschuk,I F Perepichka,O D Parashchuk,M S Pshenichnikov,P H M Van Loosdrecht

doi:10.1051/epjconf/20134105036

Abstract

We study charge recombination rates in blends of MEH-PPV and a comprehensive set of low molecular-weight fluorine-based acceptors, using visible-pump - IR-probe photoinduced absorption technique. The positions of acceptor’s HOMO-LUMO levels are engineered by addition of different chemical substituents. The results clearly show the exponential scaling of the charge recombination rate with the acceptor LUMO energy. The minimal donor-acceptor LUMO energy difference required to form a CTC state is estimated as ∼ 0.25 eV.

Highlights

We study charge recombination rates in blends of MEH-PPV and a comprehensive set of low molecular-weight fluorine-based acceptors, using visiblepump – IR-probe photoinduced absorption technique
The results clearly show the exponential scaling of the charge recombination rate with the acceptor LUMO energy
The ground-state charge transfer complexes (CTCs) are characterized by a partial shift of electronic density from the donor to the acceptor molecule already in the ground state

Summary

Introduction

We study charge recombination rates in blends of MEH-PPV and a comprehensive set of low molecular-weight fluorine-based acceptors, using visiblepump – IR-probe photoinduced absorption technique. The results clearly show the exponential scaling of the charge recombination rate with the acceptor LUMO energy. The minimal donor-acceptor LUMO energy difference required to form a CTC state is estimated as ~0.25 eV.

Results

Conclusion