EP02.12.02 : Carrier Delocalization and Long-Lived Charges in Doped Conjugated Polymers

2:00 PM–2:30 PM Apr 5, 2018 (America - Denver)

PCC North, 200 Level, Room 222 BC

Garry Rumbles1 2 3

1, NREL, Lakewood, Colorado, United States
2, University of Colorado Boulder, Boulder, Colorado, United States
3, University of Colorado Boulder, Boulder, Colorado, United States

This presentation will focus on understanding the fundamental steps of photoinduced electron transfer in thin films conjugated polymers doped with low concentrations of molecular electron acceptors. The goal is to understand how these systems produce very high yields of long-lived, separated charges when exciting the acceptor directly, or indirectly through the conjugated polymer, which can serve as both a light harvesting antenna system and electron donor. An unusual feature of these systems is the large discrepancy in timescales of the initial photoinduced electron transfer step, which is sub-picosecond, and the recombination process, which can take as long as milliseconds.
By controlling the solid-state microstructure of the conjugated polymer through the degree of regioregularity, or by changing sample temperature we demonstrate how the yield of long-lived carriers, detected by transient microwave and optical absorption spectroscopies, is controlled by the delocalization effect afforded by regions of order within the polymer film. The influence that this control exerts on the carrier recombination process through the formation of a long-lived, emissive exciplex state will also be discussed.