Search

Aryl-substituted phenanthroimidazoles (PIs) have attracted tremendous attention in the field of organic light-emitting diodes (OLEDs), because they are simple to synthesize and have excellent thermal properties, high photoluminescence quantum yields (PLQYs), and bipolar properties. Herein, a novel blue-green emitting material, ( E)-2-{4′-[2-(anthracen-9-yl)vinyl]-[1,1′-biphenyl]-4-yl}-1-phenyl-1 H-phenanthro[9,10- d]imidazole (APE-PPI), containing a t-APE [1-(9-anthryl)-2-phenylethene] core and a PI moiety was designed and synthesized. Owing to the PI skeleton, APE-PPI possesses high thermal stability and a high PLQY, and the compound exhibits bipolar transporting characteristics, which were identified by single-carrier devices. Nondoped blue-green OLEDs with APE-PPI as the emitting layer show emission at λ=508 nm, a full width at half maximum of 82 nm, a maximum brightness of 9042 cd m−2, a maximum current efficiency of 2.14 cd A−1, and Commission Internationale de L'Eclairage (CIE) coordinates of (0.26, 0.55). Furthermore, a white OLED (WOLED) was fabricated by employing APE-PPI as the blue-green emitting layer and 4-(dicyanomethylene)-2- tert-butyl-6-(1,1,7,7-tetramethyljulolidin-4-yl-vinyl)-4 H-pyran (DCJTB) doped in tris-(8-hydroxyquinolinato)aluminum (Alq3) as the red-green emitting layer. This WOLED exhibited a maximum brightness of 10029 cd m−2, a maximum current efficiency of 16.05 cd A−1, CIE coordinates of (0.47, 0.47), and a color rendering index (CRI) of 85. The high performance of APE-PPI-based devices suggests that the t-APE and PI combination can potentially be used to synthesize efficient electroluminescent materials for WOLEDs. [ABSTRACT FROM AUTHOR]

Single layer structure is an ideal way to realize the low cost solution processed organic light-emitting diodes (OLEDs). Efficient electroluminescent material with hole and electron transport characters as well as suitable triplet energy levels is highly desired to realize single layer OLEDs with good performance. In this work, a bipolar compound with carbazole as electron donor and 4,5-diphenylimidazoleas as electron acceptor has been successfully synthesized and applied as emitting layer for both non-doped and doped single layer OLEDs fabricated by solution processing. A pure blue emission achieved in the non-doped single layer OLED with a current efficiency of 0.38 cd A −1 , luminance up to 672 cd m −2 . The single layer doped OLEDs with the bipolar compound as host achieved blue, green and red phosphorescence OLEDs with current efficiency of 0.083, 13.42, 2.58 cd A −1 and luminance up to 108, 17103, 1347 cd m −2 , respectively. The performance of single layer OLEDs has been greatly improved by bipolar emitting materials which show a great potential to simplify the configuration of OLEDs. [ABSTRACT FROM AUTHOR]