Microstructural Model of Indacenodithiophene-co-benzothiadiazole Polymer: π-Crossing Interactions and Their Potential Impact on Charge Transport

Abstract

Morphological and electronic properties of indacenodithiophene- co -benzothiadiazole (IDTBT) copolymer with varying molecular weights are calculated through combined molecular dynamics (MD) and quantum chemical (QC) methods. Our study focuses on the polymer chain arrangements, interchain connectivity pathways, and interplay between morphological and electronic structure properties of IDTBT. Our models, which are verified against GIWAXS measurements, show a considerable number of BT-BT π–π interactions with a (preferential) perpendicular local orientation of polymer chains due to the steric hindrance of bulky side chains around IDT. Although our models predict a noncrystalline structure for IDTBT, the BT-BT (interchain) crossing points show a considerable degree of short-range order in spatial arrangement which most likely result in a mesh-like structure for the polymer and provide efficient pathways for interchain charge transport.

From Chemical Drawing to Electronic Properties of Semiconducting Polymers in Bulk: A Tool for Chemical Discovery

“…We previously verified the quality of the models generated by the workflow shown in Scheme and equilibrated through the “melt” method for IDT-BT, where a strong agreement between the simulated X-ray scattering patterns from our models and the pattern given by GIWAXS measurement was achieved, see Figure 2 in ref . Similar analyses on the microstructures of two DPP-based (i.e., DPP-2TT and DPP-DTT) and two BT-based (i.e.. IDT-BT and TIF-BT) models obtained from “melt” equilibration have been done, and a comparison with experimental data is discussed in Section S2.2 of the Supporting Information, demonstrating that a single workflow can be successfully validated across a class of materials.…”

“…After calculating the force field parameters for the minimal model (representing the backbone of the polymer), the side chains are attached to the designated positions, i.e., all methyl groups in the minimal polymer model, the side-chain force field parameters (united-atom and directly taken from OPLS-FF) are added, and the atomic charges around the side chain-backbone connection points are corrected to maintain the whole repeat-unit charge neutrality (step 4 in Scheme ), see Supporting Information, Section S1.3. Last, polymer chain models (i.e., coordinates and force field files) with desired degrees of polymerization (e.g., in this study n = 10 since the effect of M w on the calculated electronic structure properties was found to be negligible from n ≥ 10) are generated (step 5 in Scheme ). Note that the Lennard-Jones parameters for all backbone atoms were also taken from the OPLS force field to be consistent with the side-chain parameters and the combination rule for the pairwise Lennard-Jones potential used in the force field is consistent with OPLS (i.e., geometric mean of the self-interaction parameters), see the formula in Supporting Information Section S1.1.1.…”

A Homopolymer of Xanthenoxanthene‐Based Polycyclic Heteroaromatic for Efficient and Stable Perovskite Solar Cells

“…The HOMO demonstrates a well‐distributed presence across the entire conjugated backbone. Furthermore, in comparison to indacenodithiophene used in high‐performance conjugated copolymers, [57–59] the relatively distant sp 3 carbons in TNI2 possibly introduce unconventional short‐ and medium‐range order as well as interchain crossing points in the segmental level [60–62] . All these features are conducive to intrachain and interchain charge transport [55,63] …”

“…Furthermore, in comparison to indacenodithiophene used in high-performance conjugated copolymers, [57][58][59] the relatively distant sp 3 carbons in TNI2 possibly introduce unconventional short-and medium-range order as well as interchain crossing points in the segmental level. [60][61][62] All these features are conducive to intrachain and interchain charge transport. [55,63] By integrating p-TNI2 as a main component in the hole transport layer, we fabricated PSCs exhibiting an impressive initial average PCE of 24.6 %, outpacing control cells featuring spiro-OMeTAD (24.4 %), p-TAA (20.3 %), and P3HT (16.8 %).…”

Improving the hole mobility of conjugated semiconducting polymer films by fast backbone aggregation during the film formation process

“…Based on the high efficiency of intrachain charge transport along the coplanar backbone of IDTBT, this morphology was devoted to enhancing the interchain charge transport to improve the electrical properties. 47–49 This is enabled by tuning the solubility difference R a (b–s) between the backbone and side-chain in the solvent. By using three solvents with different R a (b–s) (chloroform > benzene > cyclohexane), we discover several different solution aggregation states and distinct aggregation behaviors in the film formation through in situ UV-vis absorption and MD simulations.…”