Efficient persistent room temperature phosphorescence in organic materials

It has been well-recognized that phosphorescence lasting longer than one second in organic materials is only observable in the frozen state at 77 K under inert conditions. This is because of several factors: Thermally activated vibrational motion of molecules, the diffusion processes between host and guest compounds and the existence of oxygen. All of these factors significantly quench the excited stable triplet states at room temperature. Here we demonstrate a design concept of organic materials showing efficient persistent room temperature phosphorescence (RTP) by suppressing non-radiative processes of the excited triplet states. We used a host-guest system composed of a secondary amino-substiruted aromatic deuterated carbon and a hydroxy steroid compound as guest and host, respectively. In these materials, efficient persistent RTP was observed, since the non-radiative process at the lowest excited triplet state of the guest compound is significantly suppressed. Quantum efficiency of persistent RTP was more than 0.1 and phosphorescence lifetime was longer than 1 s for RGB colors.