Ambipolar Charge Transport in α-Oligofurans: A Theoretical Study

The molecular scale charge transport has been investigated in a few recently synthesized molecular crystals of alpha-oligofuran via thermally activated hopping mechanism described by the semiclassical Marcus theory. The microscopic order parameters such as reorganization energy and hopping matrix elements, governing charge transfer phenomena, are estimated accurately using quantum chemical calculations. The dispersion corrected density functional calculations are carried out to capture the weak van der Waal interactions between the pi-stacked molecules. The hopping matrix elements or charge transfer integrals are computed as the off-diagonal elements of Kohn-Sham matrix using fragment orbital approach which explicitly considers the spatial overlap between the molecular orbitals. Our study reveals that such oligofuran molecular crystals are excellent conductors for both charge carriers, However, the hole mobility is found to be slightly larger than electron mobility in smaller oligofuran molecular crystals, whereas the reverse holds true for larger molecule. Such ambipolar organic crystals with higher electron mobility show the possibility of sophisticated device fabrication in advanced electronics. In addition, we compare all our results with analogous oligothiophene crystals by performing the same level of calculations.