Analysis of unusual temperature dependence of Ir complexes

我们建立了一个基于积分球的绝对PL量子效率测量系统。我们仔细测量了绝对PL量子效率和内部系统交叉（ISC）效率的Ir配合物，这是有用的有机发光二极管。特别地，我们阐明了从三重激发态到基态的非辐射衰减过程，观察到发射绿色光的Ir（ppy）_3的PL量子效率η <PL>=89± 2%，发射蓝色光的FIrpic的PL量子效率η <PL>=89± 2%，表明它们的掺杂抑制了非辐射衰减过程。而Btp_2Ir（acac）的发射率则很低，η <PL>=32± 3%。为了阐明非辐射失活过程，我们用光声光谱（PAS）测量ISC效率。结果表明，Btp_2Ir（acac）具有接近100%的ISC效率，并且我们得出三重态能级的非辐射失活效率为64%。

We established an absolute PL quantum efficiency measurement system using an integrating sphere. We carefully measured absolute PL quantum efficiency and internal system crossing (ISC) efficiency of Ir complexes which are useful for organic light emitting diodes. In particular, we clarified non-radiative decay process from the triplet excited state to the ground state.We observed that green emitting Ir(ppy)_3 has PL quantum efficiency of η_<PL>=89±2%, and blue emitting FIrpic has η_<PL>=89±2%, indicating suppression of non-radiative decay processes in their doped films. On the other hand, red emitting Btp_2Ir(acac) showed rather low η_<PL>=32±3%. In order to clarify the non-radiative deactivation process, we measured the ISC efficiency by photoacoustic spectroscopy (PAS). As a result, Btp_2Ir(acac) was revealed to have nearly 100% of ISC efficiency, and we concluded that non-radiative deactivation efficiency from the triplet level is 64%.