Pyreno[4,5‐d]imidazole‐triazatruxene Dyads for OLED Applications

Abstract

Two new structural isomers of pyreno[4,5‐d]imidazole‐triazatruxene (C‐Pyl‐TAT and N‐Pyl‐TAT) were successfully synthesized via microwave‐assisted Suzuki cross‐coupling reaction. The target compounds were characterized by 1H‐NMR, 13C‐NMR and MALDI‐TOF mass spectroscopy. These compounds emitted blue fluorescence signals with maxima wavelengths around 434 and 436 nm in toluene solution. They exhibited good film‐forming properties and thermal stabilities with glass‐transition temperature (Tg) and decomposition temperature (T5d) above 128 °C and 390 °C, respectively. The solution‐processed Alq3‐based devices with the structure of ITO/PEDOT:PSS/HTL/Alq3/LiF:Al were fabricated to evaluate the hole‐transporting properties of these compounds. The performance of the device with C‐Pyl‐TAT as a hole‐transporting layer (HTL) showed a low turn‐on voltage of 2.8 V, a high external quantum efficiency of 1.07 %, and a maximum luminance of 19,770 cd m−2. Moreover, the use of spin‐casted films of 1,3‐bis(N‐carbazolyl)benzene doped with C‐Pyl‐TAT or N‐Pyl‐TAT as blue‐emitting materials in OLED devices were also demonstrated.