Fig. 3: Morphological and spectroscopic characterisation for the orientation of α-6T thin films.

a Absorbance spectra for α-6T thin films with different molecular orientations where the lying molecules show the highest absorbance and the mixed orientation film lies in between the lying and standing samples. b Photoluminescence (PL) spectra normalised with the absorbance at the excitation wavelength of 450 nm for α-6T thin films with different molecular orientations where the PL quenching is observed in the mixed molecules. c Time-correlated single photon counting for α-6T thin films with different molecular orientations (standing, mixed and lying) revealing a faster PL decay in the presence of both standing and lying orientations. The grey dots indicate the prompt decay (instrument response function), which in the case of the mixed and lying orientations induces an artefact at 1.3 ns. d–f Grazing-incidence wide-angle X-ray scattering (GIWAXS) diffraction images showing that the molecular orientation of α-6T thin films can be tuned with specific processing conditions. The peaks indicated by red and blue circles originate from crystallites with standing and lying molecules, respectively. g–i, schematic morphology for α-6T thin films with different molecular orientations (standing, mixed, and lying).