Wet-process organic light-emitting diodes (OLEDs) are crucial to realize cost-effective and large-area roll-to-roll fabrication of high quality displays and lightings. In this study, a wet-process feasible carbazole based host material, 2-[4-(carbazol-9-yl)butyloxy]-9-[4-(carbazol-9-yl)butyl]carbazole (6), is synthesized, and two other carbazole hosts, 2-[5-(carbazol-9-yl)pentyloxy]-9-[5-(carbazol-9-yl)pentyl]carbazole (7) and 2-[6-(carbazol-9-yl)hexyloxy]-9-[6-(carbazol-9-yl)hexyl]carbazole (8) are also synthesized for comparison. All three host materials exhibit high triplet energy, and possess high solubility in common organic solvents at room temperature. Doping a green phosphorescent emitter fac tris(2-phenylpyridine)iridium (Ir(ppy)3) into host 6 , the device shows an efficacy of 51 lmW-1 and current efficiency of 52 cdA-1 at 100 cdm-2 or 30 lmW-1 and 40.7 cdA-1 at 1,000 cdm-2. The high efficiency may be attributed to the host possessing an effective host-to-guest energy transfer, the ability for excitons to generate on both host and guest, and excellent film integrity.