Phosphorescence decay mechanism of Ir(ppy)₃ in a solid matrix

The phosphorescence intensities of the green phosphor fac tris(2-phenylpyridine) iridium [Ir(ppy)₃] in a polymethylmethacrylate [PMMA] host matrix are independent of temperature, while the phosphorescence lifetimes increase significantly at temperatures below T ∼ 50 K. In this paper, we propose a phosphorescence decay mechanism for Ir(ppy)₃ to rationalize the characteristic temperature dependence of the transient phosphorescence. By comparing a numerical model with the experimental data, we demonstrate that mutual energy transfer between the sub-levels of triplet states can explain the characteristic temperature dependence.