Cu substitution boosts self-trapped exciton emission in zinc-based metal halides for sky-blue light-emitting diodes

The PLQY of Cu:(PEA) 2 ZnX 4 metal halides was greatly boosted after Cu substitution and photophysical mechanisms are revealed. Further, Cu:(PEA) 2 ZnX 4 was used as the active layer and sky-blue light-emitting diodes were prepared for the first time.