Sequential-Twice-Doping Approach toward Synergistic Optimization of Carrier Concentration and Mobility in Thiophene-Based Polymers

The chemical doping of polymer semiconductors represents a powerful strategy for advancing organic electronic applications. However, there remains an issue in that dopants tend to disrupt the molecular packing of conjugated polymers and cause low doping efficiency in a conventional chemical doping process. In this work, we provide a sequential-twice-doping (STD) approach, in which the polymer is doped twice, sequentially by a single-solution doping (predoping) process and an immersion doping (postdoping) process. By employing an STD approach, the destruction of the original polymer packing upon doping can be avoided, and the doping efficiency is simultaneously maximized. As a result, the thiophene-based polymer with a large pi-conjugated backbone shows a high electrical conductivity of up to 408 S cm(-1) attributed to its high mobility and high carrier concentration. It is proved that the predoping process mainly endows the doping reaction occurring in the amorphous region and ensures moderate crystalline domains for charge transport. Then, the postdoping process significantly improves the doping efficiency as well as the carrier mobility without interference in the film morphology built by the predoping process. The results suggest that the STD approach is an efficient strategy toward optimizing polymer crystallinity and to achieve electrical

Automated summary

Polymer semiconductors can benefit from chemical doping, but this often disrupts the molecular packing. In this study, a sequential-twice-doping (STD) approach is proposed to avoid this issue and maximize doping efficiency. The results show that the STD approach can optimize polymer crystallinity and achieve high electrical conductivity.