Self-assembled monolayer-based blue perovskite LEDs.

Blue perovskite light-emitting diodes (LEDs) have shown external quantum efficiencies (EQEs) of more than 10%; however, devices that emit in the true blue-those that accord with the emission wavelength required for Rec. 2100 primary blue-have so far been limited to EQEs of ~6%. We focused here on true blue emitting CsPbBr colloidal nanocrystals (c-NCs), finding in early studies that they suffer from a high charge injection barrier, a problem exacerbated in films containing multiple layers of nanocrystals.