Charge recombination in CuPc/PTCDA thin films.
The recombination kinetics of photogenerated charge carriers in perylene-3, 4, 9, 10-tetracarboxylic dianhydride (PTCDA) and copper phthalocyanine (CuPc) thin films grown by organic molecular beam deposition have been studied using transient absorption spectroscopy. Optical excitation is observed to generate long-lived polaron states, which exhibit power law recombination dynamics on time scales from microseconds to milliseconds. Studies as a function of excitation density and temperature, and comparison between heterostructures and PTCDA single layers, all indicate that this power law behavior results from trapping of PTCDA- polarons in localized states, with an estimated trap state density of approximately 6 x 10(17) polarons cm(-3). This recombination behavior is found to be remarkably similar to that previously observed for polymer/fullerene blends, suggesting that it may be generic to a range of semiconducting materials.
Heutz
S
S
Centre for Electronic Materials and Devices, Department of Chemistry, Imperial College London, London SW7 2AZ, United Kingdom. s.heutz@ucl.ac.uk
Nogueira
A F
AF
Durrant
J R
JR
Jones
T S
TS