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We report a detailed characterization of the thin film morphology of all-polymer blend devices by applying a combined analysis of physical, chemical, optical, and charge transport properties. This is exemplified by considering a model system comprising poly(3-hexylthiophene) (P3HT) and poly(9,9-dioctylfluorene-co-benzothiadiazole) (F8BT). We show that the interactions between the two conjugated polymer components can be controlled by pre-forming the P3HT into highly ordered nanowire structures prior to blending with F8BT, and by varying the molecular weight of the F8BT. As a result, it is possible to produce films containing highly ordered P3HT with hole mobilities enhanced by three orders of magnitude over the pristine blends. Raman spectroscopy under resonant excitation conditions is used to probe the molecular order of both P3HT and F8BT phases within the blend films and these morphological studies are complemented by measurements of photocurrent generation. The resultant increase in photocurrent is associated with the enhanced charge carrier mobilities. The complementary analytical method demonstrated here is applicable to a wide range of polymer blend systems for all applications where the relationships between morphology and device performance are of interest. [ABSTRACT FROM AUTHOR]

The relationship between the electrical properties and the microstructure of poly(3-hexylthiophene) (P3HT) films doped with an electron acceptor, 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4-TCNQ) has been studied. The introduction of F4-TCNQ in very small quantities improved the device performance of P3HT thin-film transistors significantly. The field-effect mobility of a device doped with only 0.2 wt % F4-TCNQ was enhanced by a factor of 30 with respect to that of a pure P3HT device. The threshold voltages of the P3HT thin-film transistors can also be controlled by adjusting the F4-TCNQ concentration. These improvements are attributed to the doping-induced formation of charge-transfer complexes and improved molecular orientation of the P3HT. [ABSTRACT FROM AUTHOR]

We investigated preferentially oriented pentacene grains on rubbed polyimide (PI) layers under various conditions, such as substrate temperature and cumulative rubbing number. In case of pentacene thin films deposited on rubbed PI at room temperature (RT), compared to unrubbed, the field-effect mobilities were improved by two- to threefold in contrast to the cases of elevated temperature. From the results of crystalline in-plane orientation and thin-film versus bulk-phase ratio, we proposed that pentacence crystalline orientation on a rubbed PI layer could be more favorable at RT, whereas the heating energy might weaken the interaction energy between pentacene molecules and aligned PI layer. [ABSTRACT FROM AUTHOR]

Indium tin oxide (ITO) substrates modified with self-assembled monolayers (SAMs) were used to control the anode work function and active layer morphology of organic solar cells based on poly(3-hexylthiophene)/[6:6]-phenyl-C61 butyric acid methyl ester heterojunctions. By using SAMs with the terminal groups –NH2, –CH3, and –CF3, the authors were able to control the hole injection barrier of the ITO closer to the highest occupied molecular orbital level of active layer and surface energy of the ITO substrate. A solar cell device with CF3 SAM treated ITO was found to exhibit high efficiency performance, about 3.15%. [ABSTRACT FROM AUTHOR]