Pandya Raj, Chen Richard Y S, Gu Qifei, Gorman Jeffrey, Auras Florian, Sung Jooyoung, Friend Richard, Kukura Philipp, Schnedermann Christoph, Rao Akshay
Department of Physics, Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, U.K.
Physical and Theoretical Chemistry Laboratory, Oxford University, South Parks Road, Oxford OX1 3QZ, U.K.
J Phys Chem A. 2020 Apr 2;124(13):2721-2730. doi: 10.1021/acs.jpca.0c00346. Epub 2020 Mar 18.
We present a statistical analysis of femtosecond transient absorption microscopy applied to four different organic semiconductor thin films based on perylene-diimide (PDI). By achieving a temporal resolution of 12 fs with simultaneous sub-10 nm spatial precision, we directly probe the underlying exciton transport characteristics within 3 ps after photoexcitation free of model assumptions. Our study reveals sub-picosecond coherent exciton transport (12-45 cm s) followed by a diffusive phase of exciton transport (3-17 cm s). A comparison between the different films suggests that the exciton transport in the studied materials is intricately linked to their nanoscale morphology, with PDI films that form large crystalline domains exhibiting the largest diffusion coefficients and transport lengths. Our study demonstrates the advantages of directly studying ultrafast transport properties at the nanometer length scale and highlights the need to examine nanoscale morphology when investigating exciton transport in organic as well as inorganic semiconductors.
我们对基于苝二酰亚胺（PDI）的四种不同有机半导体薄膜进行了飞秒瞬态吸收显微镜的统计分析。通过实现12飞秒的时间分辨率和同时低于10纳米的空间精度，我们在光激发后3皮秒内直接探测潜在的激子传输特性，无需模型假设。我们的研究揭示了亚皮秒级的相干激子传输（12 - 45厘米/秒），随后是激子传输的扩散阶段（3 - 17厘米/秒）。不同薄膜之间的比较表明，所研究材料中的激子传输与它们的纳米级形态密切相关，形成大晶域的PDI薄膜表现出最大的扩散系数和传输长度。我们的研究证明了在纳米长度尺度直接研究超快传输特性的优势，并强调了在研究有机和无机半导体中的激子传输时检查纳米级形态的必要性。
