High-performance deep-blue emitting phenanthroimidazole derivatives with a structure of donor−linker−acceptor were designed and synthesized. By using different linkers and different linking positions, four deep-blue emitters were obtained and used as emitters or bifunctional hole-transporting emitters in OLEDs. Such devices show low turn-on voltages (as low as 2.8 V), high efficiency (2.63 cd/A, 2.53 lm/W, 3.08%), little efficiency roll-off at high current densities, and stable deep-blue emissions with CIE y < 0.10. Performances are among the best comparing to recently reported deep-blue emitting devices with similar structures. The results suggest that the combination of the phenanthroimidazole and the donor−linker− acceptor structure can be an important approach for developing high performance deep-blue emitters in particular for lighting applications. KEYWORDS: high efficiency, nondoped, deep-blue organic light emitting devices ■ INTRODUCTION Blue organic light-emitting devices (OLEDs) have attracted much attention for their importance in both full-color display and solid-state lighting. 1 Given that phosphorescent OLEDs can theoretically achieve 100% internal quantum efficiency, many researchers have reported phosphorescent materials with high efficiency deep-blue emission. 2 However, phosphorescence OLEDs typically have shorter lifetime and sharper efficiency roll-off at high brightness. Thus, phosphorescence and fluorescence OLEDs are often considered to be complementary and suitable for different applications. On the other hand, many high performance OLEDs involve doping of emitters into host materials. 3 However, efficacious doping often requires precise control of doping concentration and inevitably increases manufacturing cost. It has also been pointed out that potential phase separation in the dopant−host system can render energy transfer ineffective. 4 For these reasons, non-doped devices using blue light-emitting fluorescent OLEDs are still attracting considerable attention. While many high efficiency blue fluorescent materials have been reported, many of them give sky-blue emissions instead of saturated blue with CIE y < 0.10. 5 On the other hand, many saturated blue emitters were designed with incorporation of the electron-withdrawing moiety for easier electron injection. However, these materials typically also have deep highest occupied molecular orbital (HOMO) leading to larger hole− injection barriers at the hole-transporter/emitter junctions and thus higher operation voltages as well as lower efficiencies.