A series of compounds containing arylamine and 1,2‐diphenyl‐1H‐benz[d]imidazole moieties are developed as ambipolar, blue‐emitting materials with tunable blue‐emitting wavelengths, tunable ambipolar carrier‐transport properties and tunable triplet energy gaps. These compounds possess several novel properties: (1) they emit in the blue region with high quantum yields; (2) they have high morphological stability and thermal stability; (3) they are capable of ambipolar carrier transport; (4) they possess tunable triplet energy gaps, suitable as hosts for yellow‐orange to green phosphors. The electron and hole mobilities of these compounds lie in the range of 0.68–144 × 10−6 and 0.34–147 × 10−6 cm2 V−1 s−1, respectively. High‐performance, single‐layer, blue‐emitting, fluorescent organic light‐emitting diodes (OLEDs) are achieved with these ambipolar materials. High‐performance, single‐layer, phosphorescent OLEDs with yellow‐orange to green emission are also been demonstrated using these ambipolar materials, which have different triplet energy gaps as the host for yellow‐orange‐emitting to green‐emitting iridium complexes. When these ambipolar, blue‐emitting materials are lightly doped with a yellow‐orange‐emitting iridium complex, white organic light‐emitting diodes (WOLEDs) can be achieved, as well by the use of the incomplete energy transfer between the host and the dopant.

Organic light-emitting diodes (OLEDs) have attracted a great deal of interest because of their potential applications in full-color flat-panel displays and lighting sources.[1] Considerable progress has been made on both small-molecule-and polymer-based OLEDs. Though blue-, green-, and redemitting materials are all needed for OLED applications, currently development of deep-blue emitters with good stability and high luminescence efficiency is deemed most critical in effectively reducing the power consumption and generating emission of different colors (including white light). In recent years considerable efforts have been shifted to the development of luminescent transition-metal complexes, particularly second-and third-row transition metals.[2] As a result of efficient spin-orbit coupling in these complexes, both singlet and triplet excitons can be harvested, and theoretically up to 100 % internal quantum efficiencies can be attained. However, metal complexes are typically crystalline and must be used as a dopant in an appropriate host. Furthermore, the host and materials used for carrier transport or carrier blocking must have sufficiently large triplet (T 1 ) energy to prevent the loss of triplet excitons from the metal complexes.[3] Therefore, phosphorescence-based devices frequently have complicated structures. Since blue-emitting phosphorescent materials have relatively a large triplet energy, it becomes increasingly difficult to find host materials with a suitably high triplet state.