In this letter, we reported the influence of solvents or UV light irradiation on EL efficiency of phosphorescence-doped PLEDs. The molecular conformation of host material PVK depended on different treatment process, which can be switched from side-by-side structure to face-to-face structure. More triplets are formed inside PVK molecular with face-to-face conformation structure that induced lower carrier transport ability. Therefore, it is significant to optimize the treatment process of phosphorescence-doped PLED to achieve higher efficiency by molecular conformation controlling.