Binaphthalene bridged bipolar transporting materials for blue electroluminescence: toward high EL efficiency via molecular tuning |
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Authors: | Rossatorn Muangpaisal Wei-I Hung Jiann T Lin San-Yu Ting Li-Yin Chen |
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Institution: | 1. Taiwan International Graduate Program, Taiwan, ROC;2. Institute of Chemistry, Academia Sinica, 128 Section 2 Academia Road, Nankang, Taipei 11529, Taiwan, ROC;3. Department of Chemistry, National Tsing Hua University, 101 Section 2 Kuang-Fu Road, Hsinchu 30031, Taiwan, ROC;4. Department of Photonics, National Sun Yat-Sen University, Kaohsiung 804, Taiwan, ROC |
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Abstract: | Two isomeric bipolar transporting molecules containing arylamine and benzimidazole moieties linked by 1,1′-binaphthalene bridge have been synthesized and used for blue light-emitting diodes. The highly twisted binaphthalene bridge is beneficial for amorphous morphology, good solubility, high thermal stability and high photoluminescence quantum efficiency (ΦPL). The charge transfer bands of these compounds exhibit interesting solvent-polarity dependent fluorescence properties. The physical properties of the compounds were tunable upon binding of the benzimidazole with binaphthalene group via C- (BINAPC) or N- (BINAPN) linkage. Three-layered blue-emitting OLEDs using BINAPC or BINAPN as the emitting layer, NPB as the hole transporting layer, and TPBI as the electron transporting layer as well as hole-blocking layer exhibit good performance. External quantum efficiencies of 2.49% with color coordinates of (0.15, 0.11) and 2.67% with color coordinates of (0.16, 0.16) were achieved for BINAPC and BINAPN, respectively. |
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Keywords: | Amorphous materials Blue light-emitting Bipolar transport Structure&ndash properties correlations Organic light emitting diode |
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