Complementary Semiconducting Polymer Blends for Efficient Charge Transport

Abstract

Charge transport in polymeric thin films is a complicated process, which involves a multitude of coupled electronic events. Because of the growing appeal of semiconducting polymers in organic electronics, it makes the fundamental understanding of charge transport increasingly important. On the other hand, it urges the solution of the processability problem, frequently associated with high-performance polymers. In this study, we introduce complementary semiconducting polymer blends (c-SPBs), aiming to provide solutions for both the fundamental understanding of charge transport and the processability problem. The c-SPBs contain a highly crystalline matrix polymer with intentionally placed conjugation-break spacers (CBSs) along the polymer backbone, thus eliminating intrachain transport, and a tie chain polymer that is a fully conjugated polymer, restoring intrachain transport by connecting π-crystalline aggregates in the matrix polymer. The results show that the addition of as little as 1 wt % tie chain polymer into the matrix polymer induces a nearly 2 order of magnitude improvement in charge carrier mobility from ∼0.015 to 1.14 cm 2 V −1 s −1 , accompanied by substantial lowering of activation energies from 100.1 to 64.6 meV. The morphological characterizations and electrical measurements confirm that tie chains are able to build the connectivity between crystalline aggregates, leading to efficient charge transport in the polymer blend films. Furthermore, this study suggests that c-SPBs can be a new platform for designing high-mobility electronic materials with enhanced solution processability for future organic electronics.

The Polymer Physics of Multiscale Charge Transport in Conjugated Systems

“…In the absence of intrachain transport, DPP‐C3 transistors exhibit a low mobility of 0.009 cm 2 V −1 s −1 , but the incorporation of as little as 1 wt % of the conjugated counterpart, DPP‐C0, provides the essential connectivity between crystallites and improves the mobility of transistors by nearly two orders of magnitude to 0.81 cm 2 V −1 s −1 . These results demonstrate that long polymer chains with effective conjugation along their backbone can provide the necessary electrically connective pathways between domains …”

“…Further highlighting the importance of intercrystallite connectivity, Zhao et al created a non-conjugated polymer, DPP-C3, by placing a propyl spacer along the backbone in the repeat unit of a conjugated diketopyrrolopyrrole (DPP)-based polymer, DPP-C0. 72 In the absence of intrachain transport, DPP-C3 transistors exhibit a low mobility of 0.009 cm 2 V −1 s −1 , but the incorporation of as little as 1 wt % of the conjugated counterpart, DPP-C0, provides the essential connectivity between crystallites and improves the mobility of transistors by nearly two orders of magnitude to 0.81 cm 2 V −1 s −1 . These results demonstrate that long polymer chains with effective conjugation along their backbone can provide the necessary electrically connective pathways between domains.…”

“…These results demonstrate that long polymer chains with effective conjugation along their backbone can provide the necessary electrically connective pathways between domains. 72 More recently, copolymers with alternating donor-acceptor structure along the backbone have garnered significant interest because, intriguingly, transistors comprising them exhibit high mobilities above 1 cm 2 V −1 s −1 despite the absence of long-range order. 63,73 Notable examples include the aforementioned IDTBT, which has significantly weaker long-range order than P3HT as evidenced by X-ray diffraction, but transistors comprising IDTBT exhibit mobilities up to 3.6 cm 2 V −1 s −1 .…”

Melt‐Processing of Complementary Semiconducting Polymer Blends for High Performance Organic Transistors

“…In this communication, we report a general strategy to make melt‐processing of semiconducting polymers attractive and practical for organic electronics, and free of the issues associated with solution‐processing methods. Our approach involves complementary semiconducting polymer blends ( c ‐SPBs), which are composed of a semiconducting matrix polymer with conjugation‐break spacers along the polymer backbone and a fully conjugated polymer that functions as a tie chain . Such a molecular design imparts a strong interaction between matrix polymers and tie chain polymers in c ‐SPBs and efficient charge transport is a result of such an interaction, being fundamentally different from the reported blends of insulating polymers/semiconducting polymers where macroscopic phase segregation is often involved.…”

Zone‐Annealing‐Assisted Solvent‐Free Processing of Complementary Semiconducting Polymer Blends for Organic Field‐Effect Transistors

“…The concept of c-SPB was previously established in our group for efficient charge transport through a combination of various morphological and electrical characterizations. [6,41] Here we use the two polymers (DPP-C0 & DPP-C5, as exhibited in Figure 1a and b) as our investigating blend, incorporating the high charge mobility of DPP-C0 and the good processability of DPP-C5. After dealing the solution-processed polymer thin film with zone annealing method, we found out larger crystalline domain structures and bigger grain sizes with decreased roughness of bottom surface.…”