Tough, Semiconducting Polyethylene‐poly(3‐hexylthiophene) Diblock Copolymers

Abstract

Semiconducting diblock copolymers of polyethylene (PE) and regioregular poly(3‐hexylthiophene) (P3HT) are demonstrated to exhibit a rich phase behaviour, judicious use of which permitted us to fabricate field‐effect transistors that show saturated charge carrier mobilities, μFET, as high as 2 × 10–2 cm2 V–1 s–1 and ON‐OFF ratios, Ion/Ioff ∼ 105 at contents of the insulating PE moiety as high as 90 wt %. In addition, the diblock copolymers display outstanding flexibility and toughness with elongations at break exceeding 600 % and true tensile strengths around 70 MPa, opening the path towards robust and truly flexible electronic components.

Structure and design of polymers for durable, stretchable organic electronics

“…111 The first example of such a material, a P3HT (2b)-b-polyethylene (PE) copolymer reached a maximum strain of 660% with a composition of 10/90% P3HT (2b)-b-PE. 112 This copolymer also exhibited impressive conduction properties. The copolymer with only 10 wt% P3HT (2b) resulted in a field-effect transistor charge mobility of 2 × 10 − 2 cm 2 V − 1 s − 1 , whereas systems with 35 wt% P3HT (2b) showed mobilities approaching those of pure P3HT.…”

“…The copolymer with only 10 wt% P3HT (2b) resulted in a field-effect transistor charge mobility of 2 × 10 − 2 cm 2 V − 1 s − 1 , whereas systems with 35 wt% P3HT (2b) showed mobilities approaching those of pure P3HT. 112 This results from the low percolation threshold, or the minimum concentration to achieve a continuous interconnecting pathway for charge transport, in the P3HT material when either blended or copolymerized with a polymer that crystallizes. These systems need only 10% P3HT to form co-continuous domains, a trend also observed in other P3HT copolymer systems.…”

“…These systems need only 10% P3HT to form co-continuous domains, a trend also observed in other P3HT copolymer systems. 112,113 It is important that the insulating polymer that is used in the copolymer is also semicrystalline, otherwise the percolation pathways can be significantly affected. An example of this comes in another system, where P3HT (2b) was compolymerized with poly(methyl methacrylate) (PMMA), an amorphous polymer, only resulting in good mobility with 40% P3HT (2b), illustrating the significant changes due to the crystallinity of the copolymer.…”

“…This result is a charge mobility of over four orders of magnitude larger, to 0.02 cm 2 V − 1 s − 1 , nearly identical to P3HT (2b). 112 As the insulator component of the copolymer is not contributing to light absorption in most of these copolymer systems, it is likely that reduced absorption in the active layer would be a significant factor in reducing the short circuit current in these blends. As such, it would be advantageous to investigate systems only comprised of conjugated, absorptive polymers.…”

Block copolymer strategies for solar cell technology

“…It is, therefore, essential to postprocess after deposition of the block copolymer thin film, as shown in Figure 20, where solvent annealing was used to order the block copolymer. 143 Mü ller et al 206 synthesized a diblock copolymer of poly(3-hexylthiophene)-block-polyethylene (P3HT-b-PE) and observed that this system has good conductive properties alongside mechanical toughness, both qualities that are desirable for flexible solar cells. Although not strictly concerned with making OPVs from this material, it shows the possibilities of a double crystalline diblock system.…”