Inkjet printing a small-molecule binary emitting layer for organic light-emitting diodes

作者：Mu, Lan; He, Mengjiao; Jiang, Congbiao; Wang, Juanhong; Mai, Chaohuang; Huang, Xiaolan; Zheng, Hua; Wang, Jian; Zhu, Xu-Hui^*; Peng, Junbiao^*

来源：Journal of Materials Chemistry C, 2020, 8(20): 6906-6913.

DOI：10.1039/d0tc00628a

• MORPHOLOGIES
• FILMS

For inkjet-printed organic light-emitting diodes, it is critical to obtain a homogeneous small molecule-based emitting film. In contrast to the conventional strategy of utilizing mixed solvents, we have successfully inkjet printed a binary electrophosphorescent emitter with a single solvent. The binary emitter consists of a new host material 3-(3,6-di-t-butylcarbazol-9-yl)-3 '-(2-(4-t-butylphenyl)benzoimidazol-1-yl)-[1,1 '-biphenyl], and an iridium complex dopant bis(2-methyldibenzo[f,h]quinoxaline)(acetylacetonate)-iridium(iii) (Ir(MDQ)(2)(acac)). Compatible with Ir(MDQ)(2)(acac), the newly developed host is highly soluble and amorphous with a glass transition temperature of 137 degrees C upon cooling from the melt. The inkjet printability and film morphology of the emitting layer are strongly dependent both on the substrates and the solvents. With o-dichlorobenzene (o-DCB) as the single solvent, and poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(4,4 '-(N-(p-butylphenyl))diphenylamine)] (TFB) as the hole transporting layer, a uniform emitter film morphology without any coffee ring is obtained. The phosphorescent OLED with the inkjet-printed emitter yields a maximum current efficiency of 17.89 cd A(-1), comparable to that of Ir(MDQ)(2)(acac)-based OLEDs with a spin-cast emitter.

• 单位
  东莞理工学院