The effects of a single atom substitution and temperature on electronic and photophysical properties F8T2 organic material

Abstract

The electronic and photophysical features of F8T2 organic semiconductor-based on a single atom substitution and temperature have been carried out by the self-consistent charge density-functional based tight-binding (SCC-DFTB) which is based on the density functional theory (DFT) and molecular dynamics (MD) methods. First of all, the heat treatment was carried out on the F8T2 from 50 K to 600 K. After that, the optoelectronic features of F8T2 by substitution of some nonmetallic single atoms, such as Fluorine (F), Bromine (Br) and Iodine (I) was studied. Herein, the dipole moments, HOMO, LUMO, bandgap and Fermi energies were searched. Also, the absorbance has been examined by time-dependent (TD)-DFTB. The obtained results of F8T2 were compared to experimental results. The HOMO value was found as-5.045 eV, which is compatible with its experimental value (-5.44 eV); the LUMO value was found-2.729 eV, which is coherent with the experimental LUMO value (-2.95 eV). Similarly, the bandgap of F8T2 (2.32 eV) was found to be compatible with measured result (2.49 eV). The bandgap for F8T2 increased from 2.32 eV (at 0 K) to 3.03 K (at 663.38 K) which is about 0.71 eV wide than that of F8T2 at 0 K. The maximum absorbance is found as 437 nm which is very well matched with experimental value (465 nm).

Ultrafast electron dynamics in excited states of conjugated thiophene–fluorene organic polymer (pF8T2) thin films

“…Theoretical calculations by Kurban predict the occupied states at E B = −5.6, −6.4, −6.7 and −7.5 eV, which agrees quite remarkably with the experimental values presented here. 73 The four uppermost states that we assign to the π-states are included as brown bars in the schematic energy level overview, see Fig. 6.…”

“…The states in orange are derived from the absorption spectra. (*) In blue are the experimental determined polaron and exciton from Yonezawa, and in grey the adapted states from the calculations of Damas et al and Kurban et al38,49,73 Arrows indicate excitation pathways at the given wavelength.…”