Ambipolar Phosphine Derivatives to Attain True Blue OLEDs with 6.5% EQE

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• 作者：Ilya Kondrasenko ; Zheng-Hua Tsai ; Kun-you Chung ; Yi-Ting Chen ; Yana Yu Ershova ; Antonio Doménech-Carbó ; Wen-Yi Hung ; Pi-Tai Chou ; Antti J. Karttunen ; Igor O. Koshevoy
• 刊名：ACS Applied Materials & Interfaces
• 出版年：2016
• 出版时间：May 4, 2016
• 年：2016
• 卷：8
• 期：17
• 页码：10968-10976
• 全文大小：554K
• 年卷期：0
• ISSN：1944-8252

文摘

A family of new branched phosphine derivatives {Ph<sub>2sub>N–(C<sub>6sub>H<sub>4sub>)<sub>nsub>−}<sub>3sub>P → E (E = O 1–3, n = 1–3; E = S 4–6, n = 1–3; E = Se 7–9, n = 1–3; E = AuC<sub>6sub>F<sub>5sub> 4–6, n = 1–3), which are the donor–acceptor type molecules, exhibit efficient deep blue room temperature fluorescence (λ<sub>emsub> = 403–483 nm in CH<sub>2sub>Cl<sub>2sub> solution, λ<sub>emsub> = 400–469 nm in the solid state). Fine tuning the emission characteristics can be achieved varying the length of aromatic oligophenylene bridge −(C<sub>6sub>H<sub>4sub>)<sub>nsub>–. The pyramidal geometry of central R<sub>3sub>P → E fragment on the one hand disrupts π-conjugation between the branches to preserve blue luminescence and high triplet energy, while on the other hand provides amorphous materials to prevent excimer formation and fluorescence self-quenching. Hence, compounds 2, 3, 5, and 12 were used as emitters to fabricate nondoped and doped electroluminescent devices. The luminophore 2 (E = O, n = 2) demonstrates excellently balanced bipolar charge transport and good nondoped device performance with a maximum external quantum efficiency (EQE<sub>maxsub>) of 3.3% at 250 cd/m<sup>2sup> and Commission International de L’Eclairage (CIE) coordinates of (0.15, 0.08). The doped device of 3 (E = O, n = 3) shows higher efficiency (EQE<sub>maxsub> of 6.5, 6.0 at 100 cd/m<sup>2sup>) and high color purity with CIE (0.15, 0.06) that matches the HDTV standard blue. The time-resolved electroluminescence measurement indicates that high efficiency of the device can be attributed to the triplet–triplet annihilation to enhance generation of singlet excitons.