We have synthesized two conjugated polymers (P1, P2) containing alternating electron-donating and -accepting units, based on N-alkyl-2,7-carbazole, 4,7-di(thiophen-5-yl)-2,1,3-benzothiadiazole and 3-[2-(4-pyridyl)vinyl]thiophene units. These conjugated polymers contained different contents of pyridine units, which were incorporated to form hydrogen bonds with [6,6]-phenyl-C-61-butyric acid (PCBA). When these hydrogen bonding interactions were present in the polymer thin films, their thermal stability improved; deterioration, which occurred through aggregation of PCBA methyl ester after lengthy annealing times, was also suppressed. The power conversion efficiency of a device incorporating the film featuring hydrogen bonding interactions remained at 75% of the original value after thermal annealing for 5 h at 140 degrees C. (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 49: 603-611, 2011