Long‐Lived and Highly Efficient TADF‐PhOLED with “(A)_n–D–(A)_n” Structured Terpyridine Electron‐Transporting Material

Abstract

The electron-transporting material (ETM) is one of the key factors to determine the efficiency and stability of organic light-emitting diodes (OLEDs). A novel ETM with a "(Acceptor) n -Donor-(Acceptor) n " ("(A) n -D-(A) n ") structure, 2,7-di([2,2′:6′,2″-terpyridin]-4′-yl)-9,9′-spirobifluorene (27-TPSF), is synthesized by combining electron-withdrawing terpyridine (TPY) moieties and rigid twisted spirobifluorene, in which the TPY moieties facilitate electron transport and injection while the spirobifluorene moiety ensures high triplet energy (T 1 = 2.5 eV) as well as enhances glass transition temperature (T g = 195 °C) for better stability. By using tris[2-(p-tolyl)pyridine]iridium(III) (Ir(mppy) 3 ) as the emitter, the 27-TPSF-based device exhibits a maximum external quantum efficiency (η ext, max ) of 24.5%, and a half-life (T 50 ) of 121, 6804, and 382 636 h at an initial luminance of 10 000, 1000, and 100 cd m −2 , respectively, which are much better than the commercialized ETM of 9,10-bis(6-phenylpyridin-3-yl)anthracene (DPPyA). Furthermore, a higher efficiency, a η ext, max of 28.2% and a maximum power efficiency (η PE , max ) of 129.3 lm W −1 , can be achieved by adopting bis(2-phenylpyridine)iridium(III) (2,2,6,6-tetramethylheptane-3,5-diketonate) (Ir(ppy) 2 tmd) as the emitter and 27-TPSF as the ETM. These results indicate that the derivative of TPY to form "(A) n -D-(A) n " structure is a promising way to design an ETM with good comprehensive properties for OLEDs.

Control of Molecular Orientation in Organic Semiconductor Films using Weak Hydrogen Bonds

“…First, we compared three types of molecules, 1 – 3 , have two terpyridine moieties which is known as electron‐acceptor units for OLEDs . Notably, these molecules had different peripheral pyridine rings.…”

Synthesis and Charge‐Transporting Properties of Dibenzothiphene Dioxide‐Based Polysiloxanes

“…But for the ESP of PDBTSi, the red region with high electron density and blue region with low electron density alternately appear on the periphery of PDBTSi. Therefore, the well alternant distribution of electron density on polymer side‐chain indicates bipolar feature, and this result illustrates that PDBTSi possesses more balanced charge transporting properties than PCzSi‐ alt ‐PDBTSi …”

A Multifunctional Bipolar Luminogen with Delayed Fluorescence for High‐Performance Monochromatic and Color‐Stable Warm‐White OLEDs

“…Luminophores with delayed fluorescence have been reported as good host materials for conventional fluorophores and phosphors, thanks to the full exciton utilization and efficient energy transfer from host to guest. [ 26 ] Herein, a representative orange phosphor, iridium(III) bis(4‐(4‐ tert ‐butylphenyl)thieno[3,2‐ c ]pyridinato‐N,C 2 ′)acetylacetonate [Ir(tptpy) 2 acac], is adopted as guest and doped into SBF‐BP‐DMAC for the fabrication of PhOLEDs. As shown in Figure A, the device architectures are ITO/HATCN (5 nm)/NPB (30 nm)/mCP (5 nm)/ y wt% Ir(tptpy) 2 acac: SBF‐BP‐DMAC (20 nm)/TPBi (50 nm)/LiF (1 nm)/Al (120 nm), y = 3, 5, and 10 for devices O1, O2, and O3, respectively.…”