Spatially resolved chiroptical study of thin films of benzo[1,2-b:4,5-b']dithiophene-based oligothiophenes by synchrotron radiation electronic circular dichroism imaging (SR-ECDi) technique

The study of the chiroptical properties of thin-film samples of two chiral benzo[1,2-b:4,5-b']dithiophene-based oligothiophenes with optoelectronic properties was carried out at Diamond B23 beamline using the synchrotron radiation electronic circular dichroism imaging (SR-ECDi) facility. The experimental results support the hypothesis that the non-reciprocal circularly polarized absorption observed in these materials is due to the combined linear dichroism and linear birefringence contributions. The mapping at 50-mu m spatial resolution revealed that several species coexist in the mesoscopic chiral domains likely due to different aggregated phases, which were identified in the films by SR-ECDi but could not be detected with benchtop ECD instruments.