Triplet-Energy Control of Polycyclic Aromatic Hydrocarbons by BN Replacement: Development of Ambipolar Host Materials for Phosphorescent Organic Light-Emitting Diodes

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• 作者：Sigma Hashimoto ; Toshiaki Ikuta ; Kazushi Shiren ; Soichiro Nakatsuka ; Jingping Ni ; Masaharu Nakamura ; Takuji Hatakeyama
• 刊名：Chemistry of Materials
• 出版年：2014
• 出版时间：November 11, 2014
• 年：2014
• 卷：26
• 期：21
• 页码：6265-6271
• 全文大小：409K
• ISSN：1520-5002

文摘

In this work, we achieved the triplet-energy control of polycyclic aromatic hydrocarbons (PAHs) by replacing the Carbon鈭扖arbon (CC) unit with a Boron鈭扤itrogen (BN) unit. Time-dependent density functional theory calculations suggested that the insertion of the BN unit may cause localization of the singly occupied molecular orbitals 1 and 2 (SOMO1/SOMO2) in the triplet state, which in turn can reduce the exchange interaction and dramatically increase the high singlet鈥搕riplet excitation energy (E_T). The PAH containing the BN unit, 4b-aza-12b-boradibenzo[g,p]chrysene, showed a large E_T value and ambipolar carrier-transport abilities. The introduction of a phenyl substituent on 4b-aza-12b-boradibenzo[g,p]chrysene slightly reduced the E_T values and the carrier-transport abilities, but increased the glass-transition temperatures. On the basis of these findings, we successfully built phosphorescent organic light-emitting diodes using the BN compounds as host materials, which exhibit a superior performance over the device using a representative host material, 4,4鈥?bis(N-carbazolyl)-1,1鈥?biphenyl, not only in terms of efficiency but also in terms of device lifetime. This study demonstrated the potential of BN-embedded polycyclic aromatics in organic electronics and showed a novel strategy to achieve triplet-energy control of aromatic compounds.