Approaching disorder-tolerant semiconducting polymers

Abstract

Doping has been widely used to control the charge carrier concentration in organic semiconductors. However, in conjugated polymers, n-doping is often limited by the tradeoff between doping efficiency and charge carrier mobilities, since dopants often randomly distribute within polymers, leading to significant structural and energetic disorder. Here, we screen a large number of polymer building block combinations and explore the possibility of designing n-type conjugated polymers with good tolerance to dopant-induced disorder. We show that a carefully designed conjugated polymer with a single dominant planar backbone conformation, high torsional barrier at each dihedral angle, and zigzag backbone curvature is highly dopable and can tolerate dopant-induced disorder. With these features, the designed diketopyrrolopyrrole (DPP)-based polymer can be efficiently n-doped and exhibit high n-type electrical conductivities over 120 S cm−1, much higher than the reference polymers with similar chemical structures. This work provides a polymer design concept for highly dopable and highly conductive polymeric semiconductors.

Thiazoloisoindigo-based ambipolar polymers for excellent balanced hole and electron mobility

“…32–34 To quantify torsional conformations and their relative contribution to the overall structural disorder, a planarity index (〈cos 2 θ 〉) was introduced as an empirical parameter. 35,36 We found that the combinations of TzII and thiophene ( θ 1 ) units, thiophene and thiophene ( θ 2 ) units, thiophene and DPP ( θ 3 ) units show high 〈cos 2 θ 1 〉, 〈cos 2 θ 2 〉, and 〈cos 2 θ 3 〉 values of 0.9326, 0.8834, and 0.9272, respectively. This result indicated the high planarization for T-TzII-T-DPP conjugated backbone would be expected owing to its high rotation barrier and low relative energy level of the conformer with the three dihedral angles of around 0°.…”

Strategic Insights into Semiconducting Polymer Thermoelectrics by Leveraging Molecular Structures and Chemical Doping

“…The other study, by X. Yan et al, designed a series of π-CPs of P(PzDPP-2FT) and P(PzDPP-4F2T) with sufficient intramolecular hydrogen bonds, which promoted the planarization of polymers, as shown in Figure 5. 67 The π-backbone of P(PzDPP-2FT) was disclosed to be zigzag curved by DFT calculations, relative to the pseudo-linear backbone of P(PzDPP-4F2T). Consistent with the guideline put forward by the previous study, the single bond connection in the torsion-susceptible linker of 4F2T led to the less planar structure of P(PzDPP-4F2T) than P(PzDPP-2FT).…”

Screening semiconducting polymers to discover design principles for tuning charge carrier mobility

“…41 The significance of the tail state distribution width and slope of the band tail has been confirmed by multiple experimental studies, where a narrower width corresponds to lower energetic disorder along the polymer backbone and higher mobilities. 28,42,43 Additionally, narrower bands in the DOS is a characteristic that could indicate higher mobility as it places charge carriers closer to the vicinity of the more delocalised states at the band edge. 44 The DOS thus provides us with a “checklist” of target features with which we can correlate atomistic features and its features which indicate high charge carrier mobility.…”