Preparation of Cyano-Substituted Tetraphenylethylene Derivatives and Their Applications in Solution-Processable OLEDs

Area of Science:

• Materials Science
• Organic Chemistry
• Optoelectronics

Background:

• High solid-state efficiency in organic luminescent materials is crucial for optoelectronic devices.
• Aggregation-induced emission (AIE) luminogens are promising for solid-state applications due to their unique photophysical properties.

Purpose of the Study:

• To design and synthesize novel AIE luminogens (AIEgens) based on 2,3,3-triphenylacrylonitrile and 2,3-diphenylfumaronitrile cores.
• To investigate the solid-state emission properties and performance of these AIEgens in non-doped organic light-emitting diodes (OLEDs).

Main Methods:

• Synthesis of AIEgens SFC and DFC (including cis- and trans-isomers) via Suzuki coupling reactions.
• Characterization of thermal stability, solubility, and photophysical properties (emission in solution and solid films).
• Fabrication and testing of non-doped OLEDs using the synthesized compounds as light-emitting layers.

Main Results:

• Synthesized AIEgens (SFC, cis-DFC, trans-DFC) are thermally stable with good solubility and exhibit weak emission in solution but strong emission in solid films.
• Introduction of an additional cyano group in DFC led to a significant red-shift in solid-state emission due to its electron-withdrawing ability.
• OLEDs fabricated with SFC showed the best performance (luminance: 5201 cd m⁻², current efficiency: 3.67 cd A⁻¹, EQE: 1.37%); trans-DFC-based OLEDs exhibited better performance than cis-DFC-based ones.

Conclusions:

• The designed AIEgens are effective for solid-state emission and can be utilized in OLEDs.
• Structural modifications, like adding cyano groups, can tune emission properties and device performance.
• The conformation of molecules in the film state influences OLED performance, as suggested by the difference between cis- and trans-DFC devices.