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Charge transfer in and conductivity of molecularly doped thiophene-based copolymers

: Ghani, F.; Opitz, A.; Pingel, P.; Heimel, G.; Salzmann, I.; Frisch, J.; Neher, D.; Tsami, A.; Scherf, U.; Koch, N.


Journal of polymer science. B, polymer physics 53 (2015), Nr.11, S.58-63
ISSN: 0887-6266
ISSN: 1099-0488
ISSN: 0098-1273
Fraunhofer IAP ()

The electrical conductivity of organic semiconductors can be enhanced by orders of magnitude via doping with strong molecular electron acceptors or donors. Ground-state integer charge transfer and charge-transfer complex formation between organic semiconductors and molecular dopants have been suggested as the microscopic mechanisms causing these profound changes in electrical materials properties. Here, we study charge-transfer interactions between the common molecular p-dopant 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane and a systematic series of thiophene-based copolymers by a combination of spectroscopic techniques and electrical measurements. Subtle variations in chemical structure are seen to significantly impact the nature of the charge-transfer species and the efficiency of the doping process, underlining the need for a more detailed understanding of the microscopic doping mechanism in organic semiconductors to reliably guide targeted chemical design.