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The Effect of Annealing on the Charge‐Carrier Dynamics in a Polymer/Polymer Bulk Heterojunction for Photovoltaic Applications
Author(s) -
Quist P. A. C.,
Savenije T. J.,
Koetse M. M.,
Veenstra S. C.,
Kroon J. M.,
Siebbeles L. D. A.
Publication year - 2005
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.200400104
Subject(s) - materials science , photoconductivity , photoexcitation , annealing (glass) , charge carrier , polymer , chemical physics , exciton , electron , heterojunction , optoelectronics , excitation , condensed matter physics , composite material , chemistry , electrical engineering , engineering , physics , quantum mechanics
The effect of annealing blends of poly(2‐methoxy‐5‐(3′,7′‐dimethyloctyloxy)‐1,4‐phenylenevinylene) (MDMO‐PPV) and a poly(cyanoether phenylenevinylene) (PCNEPV) on the photoconductivity is studied. Charge carriers are generated by pulsed‐laser excitation and their mobility and decay kinetics are monitored using time‐resolved microwave conductivity (TRMC) measurements. Photoexcitation leads to the formation of an exciton, which can undergo charge separation at an interface between the electron‐donating MDMO‐PPV and the electron‐accepting PCNEPV. The electrons and holes formed in this way must escape from each other to contribute to the photoconductivity. The photoconductivity of the blends is found to increase by almost two orders of magnitude upon thermal annealing for three hours at 100 °C. This increase is attributed to the occurrence of phase separation in the polymer/polymer film, resulting in PCNEPV‐rich parts. The formation of PCNEPV‐rich parts allows the electron to diffuse away from the interface, which favors escape from geminate recombination, leading to a higher photoconductivity.