Temperature/time-dependent crystallization of polythiophene: fullerene bulk heterojunction films for polymer solar cells.

We report the temperature/time-dependent crystallization of poly(3-hexylthiophene) (P3HT) in blend films of P3HT and [6,6]-phenyl-C(61)-butyric acid methyl ester (PC₆₁BM). The crystallization behaviour of P3HT:PC₆₁BM blend films was measured as a function of annealing time at two different temperatures (150°C and 160°C) by employing a synchrotron-radiation grazing-incidence angle X-ray diffraction (GIXD) technique. The crystallization behaviour was correlated with corresponding solar cells annealed under the same conditions. Results showed that the trend of device performance was almost in accordance with that of the (100) GIXD intensity, indicating that the nanostructure change in blend films does affect the device performance. However, the intermediate zones related to nanomorphology fluctuations, which were observed for lower temperature (140°C) annealing, were significantly suppressed at higher temperature (150°C and 160°C) annealing.