Detailed studies on energy loss mechanism in phosphor-sensitized fluorescent polymer light-emitting devices

摘要

We studied the main energy loss mechanism in electroluminescent (EL) processes in phosphor-sensitized fluorescent polymer light-emitting devices. The used organometallic phosphor is fac-tris(2-phenyl-pridine) iridium [Ir(ppy)_3] and the used red fluorescent dye is 4-(dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetrame-thyljulolidyl-9-enyl)-4H-pyran (DCJTB). The investigation found that due to the stronger electron trapping ability of DCJTB than that of Ir(ppy)_3, the excitons prefer to form on DCJTB molecules. The charge trapping on the DCJTB molecules obviously restrain the function of the phosphor-sensitizer Ir(ppy)_3. Moreover, the energy transfer from phosphorescent triplet state (T_p) to the fluorescent triplet state (T_f) also has great negative impact on the phosphor-sensitized fluorescent process. We clearly demonstrated these energy loss processes by steady-state and transient photoluminescence and comparison of device efficiency.