Morphology Control in PDVT-10/DTCP Hybrid Films via Meniscus-Guided Cooperative Crystallization for High-Performance OFETs

The meniscus-guided coating (MGC) method was used to prepare well-aligned films of hybrid systems composed of the conjugated polymer poly{3,6-dithiophen-2-yl-2,5-di(2-decyltetra-decyl)-pyrrolo[3,4-<i>c</i>]pyrrole-1,4-dione-<i>alt</i>-thienylenevinylene-2,5-yl} (<b>PDVT-10)</b> and a photoresponsive small molecule dopant, dithienylperfluorocyclopentene (<b>DTCP</b>), at various concentrations in their open-ring form (<b>DTCP-o</b>) or closed-ring (<b>DTCP-c</b>) form. The structures of the coated films were characterized with polarized optical microscopy (POM), grazing-incidence X-ray diffraction (GIXRD), and atomic force microscopy (AFM). The <b>DTCP</b> can undergo reversible isomerization between a more twisted open-ring form and a more conjugated closed-ring form under UV and visible light, respectively. Both <b>DTCP</b> isomers were found to function as morphology-modulating additives that facilitate cooperative crystallization, an effect attributed to enhanced solution-phase molecular association, which impacts the packing of the polymer film. Organic field-effect transistors (OFETs) were fabricated from these films. The <b>DTCP-c</b> doping progressively enhanced charge transport, reaching the highest mobility of 2.44 cm² V^-1 s^-1 at 10 wt %. Notably, 3 wt % <b>DTCP-o</b>, typically considered insulating molecule, increased <b>PDVT-10</b> mobility from 2.12 to 3.23 cm² V^-1 s^-1. This improvement is suggested to arise from the combined effects of precise molecular alignment by the MGC method and a favorable HOMO-HOMO energy level alignment predicted by DFT, enabling cooperative charge transfer despite the nominally insulating nature of the open-ring form. The photoswitchable <b>DTCP</b> provides a unique opportunity to optically modulate frontier molecular orbital energy levels, thereby opening up an avenue for designing electronic devices such as photocontrollable OFETs.