The impact of thermal annealing on the growth of crystalline nanodomains of poly(3-alkylthiophene) (P3AT) in thin films (15−20 nm thick) was investigated as a function of length of alkyl side chain by combined low-dose highresolution transmission electron microscopy (HR-TEM) and grazing incidence X-ray diffraction (GIXD). Statistical analysis of the data yields the characteristic dimensions of the face-on oriented P3AT nanocrystals, i.e., average stem length l c along backbones and lateral dimension perpendicular to the stems l a along side chains. The following trends were identified: (i) in as-spin-coated films, the proportion of face-on oriented nanocrystals increases with the number of carbon atoms in the side chain, (ii) annealing favors the lateral in-plane growth of the nanocrystals along the side chain direction (a P3AT axis), (iii) for a given P3AT, the proportion of face-on oriented domains increases with annealing temperature, (iv) lateral growth along the a P3AT axis is most efficient for the longer octyl side chains, and (v) thermal annealing induces only modest lamellar thickening which is limited by the poor slide diffusion of π-stacked P3AT chains as opposed to lateral growth favored by weak van der Waals interactions between layers of n-alkyl side chains. The increase in the population of face-on oriented crystallites, observed when the length of the side chain increases, coincides with a corresponding decrease in the field effect mobility in annealed P3AT thin films.

The hidden structural properties of semicrystalline polymer films are revealed by nanofocused X-ray scattering studies. X-ray cross-correlation analysis (XCCA) is employed to diffraction patterns from blends of poly(3-hexylthiophene) (P3HT) with gold nanoparticles (AuNPs). Spatially resolved maps of orientational distribution of crystalline domains allow us to distinguish sample regions of predominant face-on morphology, with a continuous transition to edge-on morphology. The average size of crystalline domains was determined to be of the order of 10 nm. As compared to pristine P3HT film, the P3HT/AuNPs blend is characterized by substantial ordering of crystalline domains, which can be induced by Au nanoparticles. The inhomogeneous structure of the polymer film is clearly visualized on the spatially resolved nanoscale 2D maps obtained using XCCA. Our results suggest that the observed changes of the polymer matrix within crystalline regions can be attributed to nanoconfinement in the presence of gold nanoparticles.

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Spatially resolved microstructural studies of operating P3HT OFET resolved by nanoGIXD.

Remarkable structural changes are reported for α,α′-DH5T oligomer thin films evaporated at different substrate temperatures and directly correlated with the electrical performance where the order of π–π stacking plays a crucial role.