Knowledge Bank

The delayed monomer and excimer fluorescence spectra of deoxygenated propylene glycol solutions of pyrene were studied from $295\circ K$ to $250\circ K$. The observed value of $\alpha$ is approximately 2 at all temperatures. It is therefore indicated that delayed fluorescence originates from triplet-triplet annihilation and that the formation of excimers and excited monomers occurs in the ratio 2:1 at different temperatures. The characteristics of delayed fluorescence and delayed excimer fluorescence of pyrene in biphenyl will also be discussed.