Annihilation-limited long-range exciton transport in high-mobility conjugated copolymer films

• 成果类型: Article
• 署名作者: Shi, Yuping; Roy, Partha P.; Higashitarumizu, Naoki; Lee, Tsung -Yen; Li, Quanwei; Javey, Ali; Landfester, Katharina; Mcculloch, Iain; Fleming, Graham R.
• 署名单位: University of California System; University of California Berkeley; United States Department of Energy (DOE); Lawrence Berkeley National Laboratory; Max Planck Society; University of California System; University of California Berkeley; United States Department of Energy (DOE); Lawrence Berkeley National Laboratory; Japan Science & Technology Agency (JST); University of California System; University of California Berkeley; University of Oxford; Princeton University; Indian Institute of Technology System (IIT System); Indian Institute of Technology (IIT) - Gandhinagar
• 刊物名称: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
• ISSN/ISSBN: 0027-11264
• DOI: 10.1073/pnas.2413850122
• 发表日期: 2025-04-29
• 关键词: field-effect transistors; semiconducting polymers; charge separation; temperature; disorder; energy; STATES

摘要

A combination of ultrafast, long-range, and low-loss excitation energy transfer from the photoreceptor location to a functionally active site is essential for cost-effective polymeric semiconductors. Delocalized electronic wavefunctions along pi-conjugated polymer (CP) backbone can enable efficient intrachain transport, while interchain transport is gen erally thought slow and lossy due to weak chain-chain interactions. In contrast to the conventional strategy of mitigating structural disorder, amorphous layers of rigid CPs, exemplified by highly planar poly(indacenodithiophene-co-benzothiadiazole) (IDT-BT) donor-accepter copolymer, exhibit trap-free transistor performance and charge-carrier mobilities similar to amorphous silicon. Here, we report long-range exciton transport in HJ-aggregated IDTBT thin-film, in which the competing exciton transport and exciton-exciton annihilation (EEA) dynamics are spectroscopically separated using a phase-cycling-based scheme and shown to depart from the classical diffusion-limited and strong-coupling regime. In the thin film, we find an annihilation-limited mec hanism with << 100% per-encounter annihilation probability, facilitating the mini mization of EEA-induced excitation losses. In contrast, excitons on isolated IDTBT chains diffuse over 350 nm with 0.56 cm2 s-1 diffusivity, before eventually annihilating with unit probability on first contact. We complement the pump-probe studies with temperature-dependent photocurrent and EEA measurements from 295 K to 77 K and find a remarkable correspondence of annihilation rate and photocurrent activation energies in the 140 K to 295 K temperature range.