image: (a) SEM image. (b) The corresponding SADE pattern. (c) The typical cryo-TEM image of the structure at high magnification. (d) GIWAXS pattern of the PDI dianion film. (e) XRD patterns of the PDI dianion aggregates and the PDI raw material.
Credit: ©Science China Press
This study is led by Professor Yuguang Ma and Qinglin Jiang (Institute of Polymer Optoelectronic Materials and Devices, State Key Laboratory of Luminescent Materials and Devices, South China University of Technology), and Associate Professor Jiang Zhang (Department of Physics, South China University of Technology).
Compared with crystalline inorganic semiconductors, organic semiconductors exhibit low carrier mobility due to weak intermolecular interactions, such as van der Waals interactions, hydrogen bonds, and π-π interactions. The intermolecular distance is large, the π-orbit overlap is small, and the electron delocalization is difficult. Increasing the π-orbit overlap between molecules is the crucial adjective way to improve the mobility of organic semiconductors. Perylenediimide and its derivatives (PDIs) have been extensively studied in organic semiconductors with n-type characteristics. PDIs molecules with the large planar conjugated structure of the perylene have strong interactions between molecules, which is beneficial to intermolecular electron delocalization but also limits the solubility of these materials.
To address this challenge, the researchers adopted the "ionization-induced reconstruction" strategy to achieve the perfect combination of intermolecular strong π-π interactions and solution processing. The PDI dianion film exhibited high Hall mobility and band-like transport characteristics due to the electronic structure of the PDI dianion (PDI2-) and the unique intermolecular interactions.
The researchers found that compared with the neutral state of PDI, the PDI2- has a high degree of electron delocalization and stronger π-π interactions (with a closer π-π stacking distance of 3.25 Å), forming an orderly arrangement of nanowire structures. The PDI dianion films exhibit a room-temperature electrical conductivity of 17 S cm-1 and p-type transporting characteristics compared to the neutral state. With a decrease in temperature, the mobility increases, and the Hall mobility reaches 3 cm2 V-1 s-1 at 150 K. The strong π-π interactions and the highly delocalized π-electrons attribute the formation of a wide bandwidth.
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See the article:
Band-like transport in solution-processed perylene diimide dianion films with high Hall mobility
https://doi.org/10.1093/nsr/nwae087
Journal
National Science Review