Deeper understanding on controlling dark and bright states in organic and perovskite LEDs

Abstract

In organic LEDs, converting dark states (triplets) into bright states (singlets) has become a crucial procedure to develop high efficiencies. Essentially, the triplet-to-singlet conversion requires a mechanism to flip the spins of triplets towards realizing the triplet-to-singlet conversion. Our recent studies have shown that charge-transfer states present a vital mechanism to generate a spin-orbital coupling (SOC) to flip spins towards converting triplets into singlets in exciplex systems. Furthermore, organic-inorganic halide perovskites are known as strong-orbital materials formed with bright (J = 1, named as triplets) and dark (J = 0, named as singlets) states. Our studies found that the orbit-orbit interaction between light-emitting states plays an important role to convert the dark states into bright states in hybrid perovskites. This presentation will discuss the SOC effects on light emission in organic and perovskite materials in spontaneous and stimulated regimes.