The morphology, optical properties, and photoconductance of blends of the poly(thienothiophene) derivatives poly(3,6-dialkylthieno[3,2-b]thiophene-co- bithiophene) (pATBT), poly(2,5-bis(3-alkylthiophen-2-yl)thieno[3,2-b]- thiophene) (pBTTT), and poly(2,5-bis(3-dodecylthiophen-2-yl)thieno[2,3-b] thiophene) (pBTCT) with [6,6]- phenyl-C61-butyric acid methyl ester (PCBM) were studied. After thermal annealing, the pATBT:PCBM blend exhibits formation of phase-segregated polymer and PCBM domains. Annealing of pBTTT:PCBM and pBTCT:PCBM yields a layered structure with PCBM molecules intercalated between layers of ?-stacked polymers. In the intercalated systems the photoluminescence is almost completely quenched, in contrast to the phase-segregated pATBT:PCBM blend. The higher degree of exciton quenching in the intercalated systems likely results in a higher initial yield of charges. However, on longer time scales (>10 ns), the microwave photoconductance for the layered systems is lower than for pATBT:PCBM blend systems. This is likely due to restricted motion of charges in intercalated systems, which reduces the yield of free charge carriers or enhances the charge carrier recombination.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Physical and Theoretical Chemistry
- Surfaces, Coatings and Films