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-c]pyrrole-1,4-dione-alt-thienylenevinylene-2,5-yl} (PDVT-10) and a photoresponsive small molecule dopant, dithienylperfluorocyclopentene (DTCP), at various concentrations in their open-ring form (DTCP-o) or closed-ring (DTCP-c) 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 DTCP 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 DTCP 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 DTCP-c doping progressively enhanced charge transport, reaching the highest mobility of 2.44 cm2 V-1 s-1 at 10 wt %. Notably, 3 wt % DTCP-o, typically considered insulating molecule, increased PDVT-10 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 DTCP 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.