Controlling Solution‐State Aggregation and Solid‐State Microstructures of Conjugated Polymers by Tuning Backbone Conformation

Abstract

Molecular ordering of conjugated polymers both in solution-state aggregates and in solid-state microstructures is a determining factor of the charge transport properties in optoelectronic devices. However, the effect of backbone conformation in conjugated polymers on assembly structures is still unclear. Herein, to understand such backbone conformation effect, three novel chlorinated benzodifurandionge-based oligo(p-phenylene vinylene) (BDOPV) polymers are systematically developed. These BDOPV-based polymers exhibit significantly twisted backbone conformation (near 90°i nterunit torsion angle) between conjugated units, which can prevent polymer chains from forming ordered assembly structures by increasing conformational energy penalty in closely packed chains. A higher rotational barrier of the torsion angle would further prevent polymer chains from assembling, finally resulting in nonaggregated chains in solution and highly disordered solid-state packing structures. This work will deepen the understanding of the relationship between polymer backbone conformation and assembly structures, contributing to the exploration of the structure-property relationship of polymers.

Role of the Chain Structure and Conformation of Conjugated Polymers on Aggregation Behavior

“…Polymers IID-2OD-2T and IID-2OD-2MT (Figure d) were developed, in which the introduction of methyl groups was expected to alter the chain conformational properties and further affect the aggregation behavior. , Density functional theory (DFT) and molecular dynamics (MD) calculations were performed first to estimate the conformation properties of both polymers, and the results were in line with our expectations (Figure e,f). The dihedral angle between MT–MT had a completely different torsional barrier from those between T–T or IID-T .…”

Effects of Halogenation of Small‐Molecule and Polymeric Acceptors for Efficient Organic Solar Cells

“…As such, the fluorinated polymer acceptors present better intramolecular conjugation and ordered chain conformation, which is anticipated to facilitate intermolecular packing for faster charge transport. [48,49] To investigate the different halogenation effects on photovoltaic performance, the abovementioned material-based devices were fabricated using the conventional device architecture of ITO/PEDOT:PSS/active layer/PNDIT-F3N/Ag by sequential deposition processing. [27,[50][51][52] The current-densityversus-voltage (J-V) curves of the devices based on the monomers and polymers are recorded in Figure 2a,d, respectively, and Table 2 presents the photovoltaic parameters of the optimized devices.…”

Synthesis and Electrical Properties of a New Bipolar Material Using Spacer Moiety

“…The methyl group of the spacer between the donor and the acceptor induced a twist, leading to a dihedral angle of 75.3 • between Cz and the spacer (Figure 3). This angle prevented the intramolecular conjugation length from increasing and inhibited intermolecular packing; thus, deep-blue emission was achieved, similar to the emission of the solution, even in the film state [22].…”

“…The methyl group of the spacer between the donor and the acceptor induced a twist, leading to a dihedral angle of 75.3° between Cz and the spacer (Figure 3). This angle prevented the intramolecular conjugation length from increasing and inhibited intermolecular packing; thus, deep-blue emission was achieved, similar to the emission of the solution, even in the film state [22]. a Toluene solution (0.5 wt%), b in thin film state (thickness: 50 nm) for DTPCZ, spin coating film (1 wt% in toluene) for poly DTPCZ; c HOMO values derived from ultraviolet photoelectron spectra (Riken-Keiki, AC-2); d optical energy band gap (E g ) estimated from the onset of the absorption spectra in a neat film at room temperature; e absolute photoluminescence quantum yield.…”