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Tetraphenylimidazole‐Based Excited‐State Intramolecular Proton‐Transfer Molecules for Highly Efficient Blue Electroluminescence

2008; Wiley; Volume: 18; Issue: 5 Linguagem: Inglês

10.1002/adfm.200700827

1616-3028

Sanghyuk Park, Jangwon Seo, Se Hun Kim, Soo Young Park,

Conducting polymers and applications

Abstract Aiming for highly efficient blue electroluminescence, we have designed and synthesized a novel class of tetraphenylimidazole‐ based excited‐state intramolecular proton‐transfer (ESIPT) molecules with covalently linked charge‐transporting functional groups (carbazole‐ and oxadiazole‐functionalized hydroxyl‐substituted tetraphenylimidazole (HPI), i.e., HPI‐Cbz and HPI‐Oxd, respectively). High T g (ca. 130 °C) amorphous films of HPI‐Cbz and HPI‐Oxd showed intense and ideal blue‐light emission ( λ max = 462 and 468 nm, Φ PL = 0.44 and 0.38) with a large Stokes shift of over 160 nm and a narrow full width at half‐maximum of less than 65 nm. Organic light‐emitting devices using HPI‐Cbz and HPI‐Oxd as the emitting layer generated an efficient blue electroluminescence (EL) emission peaking at around 460 nm with excellent CIE coordinates of ( x , y ) = (0.15, 0.11). A maximum external quantum efficiency of 2.94%, and a maximum brightness of 1 229 cd m −2 at 100 mA cm −2 , as well as a low turn‐on voltage of 4.8 V were achieved in this work.