Dresden Integrated Center for Applied Physics and Photonic Materials (IAPP) and Institute for Applied Physics , Technische Universität Dresden , Nöthnitzer Straße 61 , 01187 Dresden , Germany.
Leibniz-Institut für Polymerforschung Dresden , Hohe Straße 6 , 01069 Dresden , Germany.
ACS Appl Mater Interfaces. 2019 Mar 27;11(12):11660-11666. doi: 10.1021/acsami.8b21865. Epub 2019 Mar 12.
p-Type molecular doping of organic materials with high ionization energies (IEs) of above 5.50 eV is still a challenge, limiting the use of doping in high-performance organic light-emitting diodes (OLEDs). Here, we investigate the molecular dopant hexacyano-trimethylene-cyclopropane (CN6-CP) with a high electron affinity of 5.87 eV as p-dopant in OLEDs. We show that CN6-CP can be used not only as a dopant in the traditional hole transport material 4,4'-cyclohexylidenebis[ N, N-bis(4-methylphenyl)benzenamine] (TAPC, IE = 5.50 eV) but also effectively dopes the host material tris(4-carbazoyl-9-ylphenyl)amine (TCTA, IE = 5.85 eV), reaching a conductivity of 1.86 × 10 S/cm at a molar ratio of 0.25. Using CN6-CP-doped TAPC as hole injection and transport layer, we achieve a low driving voltage of 2.92 V at the practical brightness of 1000 cd/m and 3.18 V at a current density of 10 mA/cm for a green phosphorescent OLED based on bis2-(2-pyridinyl- N)phenyl- Ciridium(III) (Ir(ppy)(acac)), together with a maximum external quantum efficiency of 18% and a luminous efficacy of 78 lm/W. The device also exhibits a very low efficiency roll-off at high luminance. Further, by directly adopting CN6-CP-doped TCTA as the injection/transport layer, the driving voltage drops to 2.78 V at 1000 cd/m and 2.93 V at 10 mA/cm. Moreover, conductivity and absorption measurements suggest that CN6-CP could also dope CBP with an IE as high as 6.05 eV. The results show that CN6-CP is an excellent p-type dopant for efficient OLEDs and possesses great potential for future application in organic optoelectronic devices.
具有高于 5.50eV 的高电离能（IE）的 p 型分子掺杂有机材料仍然是一个挑战，限制了掺杂在高性能有机发光二极管（OLED）中的应用。在这里，我们研究了具有 5.87eV 高电子亲和力的分子掺杂剂六氰基-三甲基环丙烷（CN6-CP）作为 OLED 中的 p 型掺杂剂。我们表明，CN6-CP 不仅可以用作传统空穴传输材料 4,4'-环己基二[N,N-双（4-甲基苯基）苯胺]（TAPC，IE=5.50eV）的掺杂剂，而且还可以有效地掺杂主体材料三（4-咔唑基-9-基苯基）胺（TCTA，IE=5.85eV），在摩尔比为 0.25 时达到 1.86×10 S/cm 的电导率。使用 CN6-CP 掺杂的 TAPC 作为空穴注入和传输层，我们在实用亮度为 1000cd/m 时实现了 2.92V 的低驱动电压，在电流密度为 10mA/cm 时实现了 3.18V 的低驱动电压基于双[2-（2-吡啶基-N）苯基-C]（乙酰丙酮基）铱（III）（Ir（ppy）（acac）的绿色磷光 OLED，同时具有 18%的最大外量子效率和 78lm/W 的光效。该器件在高亮度下也表现出非常低的效率滚降。此外，通过直接采用 CN6-CP 掺杂的 TCTA 作为注入/传输层，在 1000cd/m 时驱动电压降至 2.78V，在 10mA/cm 时驱动电压降至 2.93V。此外，电导率和吸收测量表明，CN6-CP 也可以掺杂 IE 高达 6.05eV 的 CBP。结果表明，CN6-CP 是一种高效 OLED 的优秀 p 型掺杂剂，在未来的有机光电设备中具有很大的应用潜力。
