Solvent Resistant Hole-Transporting Thin Films via Diacetylene Cross-Linking and Their Applications in Solution-Processed QLEDs

A diacetylene-based thermal cross-linking method for hole-transporting layers (HTLs) has been investigated. The thin films of 4,4-bis(carbazol-9-yl)biphenyl (CBP) oligomers functionalized with diacetylene groups were cross-linked at 150 °C. The cross-linked thin films showed smooth surface morphologies and solvent stabilities in chloroform, chlorobenzene, indane, 3,5-dimethylanisole, and so on. The quantum dot light-emitting diode (QLED) devices based on the cross-linked HTLs displayed high current density, large maximum brightness, long device lifetime, and comparable external quantum efficiency in comparison with the corresponding devices based on the pristine HTLs. The hole-transporting properties of the cross-linked and the pristine HTLs were also studied in hole-only devices (HODs). This cross-linking method could be potentially useful in solution fabrication of multilayer organic electronic devices.