A DFT study on optical, electronic, and charge transport properties of star‐shaped benzo[1,2‐b:3,4‐b′:5,6‐b″]trithiophene oligomers

Abstract

We present a study of optical and electronic properties along with reorganization energies in benzo[1,2-b:3,4-b′:5,6-b″]trithiophene (BTT) and its oligomers.The primary objective of this work is to study the effect of the addition of BTT units to the core BTT, on the absorption, electronic, and charge transport properties, using density functional theory (DFT) calculations. The absorption spectra of all molecules were calculated by employing time-dependent DFT (TDDFT) methodology. The results show that the highest occupied molecular orbital (HOMO), lowest unoccupied molecular orbital (LUMO), HOMO-LUMO energy gap, ionization potentials (IPs), electron affinities (EAs), and reorganization energies (λ) are dramatically affected upon the addition of each BTT unit to the core BTT.

Density functional theory and time‐dependent density functional theory studies on optoelectronic properties of fused heterocycles with cyclooctatetraene

“…From Equation (2), it is clear that the K depends on λ and it is inversely proportional to λ. 29 The hole and electron reorganization energies (λ h and λ e ) can be calculated from Equations (3a) and (3b), [23][24][25][26]30 and the detailed procedure is given in the supporting information S1.…”

“…Molecular structures of 15 possible isomers of COF (X is O), COTh (X is S), and COSe (X is Se) molecules Also, we have calculated adiabatic and vertical ionization potentials (IP a and IP v ), and adiabatic and vertical electron affinities (EA a and EA v ) as in our previous works. [24][25][26][27]31 RESULTS AND DISCUSSION…”

“…23,24 Further study is extended for comparative study of BTT isomer with different fused heterocycles such as pyrrole (BTP), furan (BTF), and selenophene (BTSe). 25 One of our recent works has shown that the COTh has 15 possible isomers and out of these 15 isomers, only five isomers have a synthesis route. 27 The calculated UV-visible absorption obtained from time-dependent density functional theory (TDDFT) simulations are reproducing the experimental absorption of known isomers.…”

Cubic Nanogrids for Counterbalance Contradiction among Reorganization Energy, Strain Energy, and Wide Bandgap

“…The λ − of L-CG reaches an inorganic-like level as low as 54 meV, which is 2 meV lower than that of representative electron transport material C 60 . 69 The results of Figure 4c showed that the λ + of newly designed CG and L-CG are 38 and 36 meV; 39 and 37 meV; 37 and 35 meV; and 28 and 26 meV smaller than the Deca-BTT, 61 GS-SITF1, 9 GSF1, and GSF2 20 reference molecules, respectively, enlightening that the CG and L-CG could be excellent/ comparable hole transport materials compared to these widebandgap molecules. Figure 4c also shows that values for λ + of CG and L-CG are only 2 and 4 meV as well as 4 and 6 meV higher than the narrow-bandgap benzothiophene 50 and Comp6 67 demonstrating that for the two nanogrids, hole mobility values may be slightly lower/comparable with that displayed by benzothiophene and Comp6.…”

“…So far, there are four mainstream ways to reduce the ROE, namely, fused cyclization, 51 ladderization, 52−54 macrocyclization, 55−60 as well as star-shaped molecules with an increase in two-dimensional conjugation. 61 However, according to the rough statistics of Liu's group, 50 molecules with small bandgaps have a better chance of obtaining smaller ROEs. While most organic semiconductors have internal ROEs greater than 100 meV, some typical p-type semiconductors such as pentacene and n-type semiconductors such as fullerene (C 60 ) 62 are reported to have ROEs of less than 100 meV.…”