Tunable self-organization in n-type liquid crystalline dibenzocoronene tetracarboxdiimides for high photoconductivity

ABSTRACT

A comprehensive study on the self-organised mesomorphism and charge-transport properties of three n-type liquid crystalline (LC) dibenzocoronene tetracarboxdiimide derivatives (Dibenzo-CDI 1, 2, 3) bearing branched alkyl chains with varied side-chain length and branching point (α or β site) has been carried out. All three Dibenzo-CDI compounds possessed high solubility in common organic solvents and low-lying lowest unoccupied molecular orbital energy levels below −4.0 eV indicating their air-stable electron-transport capacity under ambient conditions. It is discovered that the side-chain length has a moderate influence on the molecular arrangement and thus leads to only limited variation of electron-transport properties. In contrast, the branching position plays a critical role on tuning molecular packing and orientation in the bulk mesophases, thereby resulting in dramatic differences in electron mobilities. Remarkably, Dibenzo-CDI 3 demonstrates good photoconductivity by time-of-flight method with high electron mobility up to 0.075 cm²/Vs, close to the highest value reported in certain n-type LC derivatives. All these results reveal that LC Dibenzo-CDI derivatives are potential candidates for high-performance solution-processable electronics, such as air-stable n-type organic field-effect transistors (OFETs) and solar cells.

Graphical Abstract

KEYWORDS:

• Low LUMO
• high electron mobility
• dibenzocoronene tetracarboxdiimides
• n-type liquid crystalline semiconductor

Acknowledgments

This work was supported by Beijing Municipal Education Commission of China (04190117025, 04190118002/048), the National Natural Science Foundation of China (21302012), Beijing Natural Science Foundation of China (2172024) and Beijing Municipal Education Commission of China (04190117021, 04190118002/65) and Doctoral Program of Guangdong Natural Science Foundation (18zxxt04, 20187612031680001). Jialing Pu and Tengzhou Yang contribute to this work equally.

Disclosure statement

No potential conflict of interest was reported by the authors.

Supplementary material

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Additional information

Funding

This work was supported by the Beijing Natural Science Foundation of China [2172024]; Beijing Municipal Education Commission of China [04190117021,04190117025]; National Natural Science Foundation of China [21302012]; Doctoral Program of Guangdong Natural Science Foundation [18zxxt04].