Abstract
By means of optical spectroscopy, Kelvin probe, and conductivity measurements, we study the -type doping of the donor polymer poly(3-hexylthiophene), P3HT, with the molecular acceptor tetrafluorotetracyanoquinodimethane, FTCNQ, covering a broad range of molar doping ratios from the ppm to the percent regime. Thorough quantitative analysis of the specific near-infrared absorption bands of ionized FTCNQ reveals that almost every FTCNQ dopant undergoes integer charge transfer with a P3HT site. However, only about 5 of these charge carrier pairs are found to dissociate and contribute a free hole for electrical conduction. The nonlinear behavior of the conductivity on doping ratio is rationalized by a numerical mobility model that accounts for the broadening of the energetic distribution of transport sites by the Coulomb potentials of ionized FTCNQ dopants.
- Received 1 February 2013
DOI:https://doi.org/10.1103/PhysRevB.87.115209
©2013 American Physical Society