In this thesis, bipolar host materials are reported to contain highly efficient green phosphorescent organic light-emitting diodes, including a new indenocarbazole moiety as a hole-transporting unit and a pyrimidine moiety as an electron-transporting unit. The new host materials showed excellent ele...
In this thesis, bipolar host materials are reported to contain highly efficient green phosphorescent organic light-emitting diodes, including a new indenocarbazole moiety as a hole-transporting unit and a pyrimidine moiety as an electron-transporting unit. The new host materials showed excellent electro and optical properties. Similarly, they exhibited outstanding thermal and morphological stability because of the high glass transition temperature (Tg) of 161 ℃ and the
decomposition temperature (Td) of 327-401 ℃. The fabricated green phosphorescent organic light-emitting diode showed excellent current and power efficiency of 77.8 cd/A and 62.8 lm/W, respectively, as well as an almost ideal external quantum efficiency of 22.3% at a brightness of 1,000 cd/m2. Additionally, highly efficient yellow phosphorescent organic light-emitting diodes(OLED) were reported with a new indenocarbazole moiety as a hole-transporting unit and a biphenyl moiety as electron-transporting unit. The new host materials demonstrated excellent morphological stability with a high glass transition temperature of 207 ℃. Simultaneously, the new host materials revealed that a triplet energy of about 2.6 eV was ideal for the transfer of the triplet energy to the yellow phosphorescent dopant. A phosphorescent yellow OLED with the new host ICBP1 (and ICBP2) and conventional yellow dopant Iridium(III)bis(4-(4-tbutylphenyl)thieno[3,2-c]pyridinato-N,C2’)acetylacetonate (Ir(tptpy)2acac) showed a low driving voltage of 3.4 V (and 3.6 V) at 1,000 cd/m2
and a maximum external quantum efficiency as high as 26.4%. The efficient performance of the phosphorescent yellow OLEDs was attributed to the ideal charge balance and high electron-transporting properties of the host materials.
Regarding the study of thermally activated delayed fluorescence (TADF), in this thesis, I report a key design concept of the reduction of the exciton lifetime without decreasing the photoluminescence quantum yield (PLQY) in TADF molecules by the introduction of a heteroatom containing pyridoindole donor moiety. The new TADF molecules with nitrogen at α- and δ-positions in the pyridoindole donor moiety were synthesized and their effects on the photophysical and electroluminescent properties were theoretically and experimentally investigated. The TADF molecule with δ-carboline donor moiety was the most favorable for a short exciton lifetime, high delayed PLQY, good blue color, and small singlet and triplet spitting compared to the generally used carbazole. The maximum external quantum efficiency (EQE) of 22.5% and good color purity with CIE color coordinates of (0.16, 0.23) was exhibited in the blue OLED using the TADF emitter, 4,5-bis(5H-pyrido[3,2-b]indol-5-yl) phthalonitrile (δ-2CbPN).
Moreover, the effectiveness of the δ-carboline donor moiety was verified in another deep blue TADF emitter, 5,5'-(2-(9H-carbazol-9-yl)-5-(4,6-diphenyl-1,3,5-triazin-2-yl)-1,3- phenylene)bis(5H-pyrido[3,2-b]indole) (CzDCbTrz). The maximum EQE of 22.0%, deep blue color and improved efficiency roll-off were attained in the CzDCbTrz based OLED. In addition, novel green TADF emitters were developed using new diindolocarbazole as a donor and 2,4,6- triphenyl-1,3,5-triazine acceptor. The new synthesized TADF emitters had high PLQYs with short exciton lifetimes (1~3 μs). In particular, the OLEDs containing our TRZ-DI emitter accomplished a maximum external quantum efficiency (EQEmax) of 29.2%.
In this thesis, bipolar host materials are reported to contain highly efficient green phosphorescent organic light-emitting diodes, including a new indenocarbazole moiety as a hole-transporting unit and a pyrimidine moiety as an electron-transporting unit. The new host materials showed excellent electro and optical properties. Similarly, they exhibited outstanding thermal and morphological stability because of the high glass transition temperature (Tg) of 161 ℃ and the
decomposition temperature (Td) of 327-401 ℃. The fabricated green phosphorescent organic light-emitting diode showed excellent current and power efficiency of 77.8 cd/A and 62.8 lm/W, respectively, as well as an almost ideal external quantum efficiency of 22.3% at a brightness of 1,000 cd/m2. Additionally, highly efficient yellow phosphorescent organic light-emitting diodes(OLED) were reported with a new indenocarbazole moiety as a hole-transporting unit and a biphenyl moiety as electron-transporting unit. The new host materials demonstrated excellent morphological stability with a high glass transition temperature of 207 ℃. Simultaneously, the new host materials revealed that a triplet energy of about 2.6 eV was ideal for the transfer of the triplet energy to the yellow phosphorescent dopant. A phosphorescent yellow OLED with the new host ICBP1 (and ICBP2) and conventional yellow dopant Iridium(III)bis(4-(4-tbutylphenyl)thieno[3,2-c]pyridinato-N,C2’)acetylacetonate (Ir(tptpy)2acac) showed a low driving voltage of 3.4 V (and 3.6 V) at 1,000 cd/m2
and a maximum external quantum efficiency as high as 26.4%. The efficient performance of the phosphorescent yellow OLEDs was attributed to the ideal charge balance and high electron-transporting properties of the host materials.
Regarding the study of thermally activated delayed fluorescence (TADF), in this thesis, I report a key design concept of the reduction of the exciton lifetime without decreasing the photoluminescence quantum yield (PLQY) in TADF molecules by the introduction of a heteroatom containing pyridoindole donor moiety. The new TADF molecules with nitrogen at α- and δ-positions in the pyridoindole donor moiety were synthesized and their effects on the photophysical and electroluminescent properties were theoretically and experimentally investigated. The TADF molecule with δ-carboline donor moiety was the most favorable for a short exciton lifetime, high delayed PLQY, good blue color, and small singlet and triplet spitting compared to the generally used carbazole. The maximum external quantum efficiency (EQE) of 22.5% and good color purity with CIE color coordinates of (0.16, 0.23) was exhibited in the blue OLED using the TADF emitter, 4,5-bis(5H-pyrido[3,2-b]indol-5-yl) phthalonitrile (δ-2CbPN).
Moreover, the effectiveness of the δ-carboline donor moiety was verified in another deep blue TADF emitter, 5,5'-(2-(9H-carbazol-9-yl)-5-(4,6-diphenyl-1,3,5-triazin-2-yl)-1,3- phenylene)bis(5H-pyrido[3,2-b]indole) (CzDCbTrz). The maximum EQE of 22.0%, deep blue color and improved efficiency roll-off were attained in the CzDCbTrz based OLED. In addition, novel green TADF emitters were developed using new diindolocarbazole as a donor and 2,4,6- triphenyl-1,3,5-triazine acceptor. The new synthesized TADF emitters had high PLQYs with short exciton lifetimes (1~3 μs). In particular, the OLEDs containing our TRZ-DI emitter accomplished a maximum external quantum efficiency (EQEmax) of 29.2%.
주제어
#Organic light emitting devices Phosphorescence Bipolar host Thermally activated delayed fluorescence
※ AI-Helper는 부적절한 답변을 할 수 있습니다.