High‐Performance Ultrapure Green CdSe/CdS Core/Crown Nanoplatelet Light‐Emitting Diodes by Suppressing Nonradiative Energy Transfer

Abstract Colloidal nanoplatelets (NPLs) are an emerging semiconductor nanocrystal in the display community due to their ultranarrow emission linewidth. Herein, an ultrapure green emitting nanocrystal light‐emitting diode (LED) based on four‐monolayer CdSe/CdS core/crown NPLs is developed. By applying the nonstacked nanoplates, the nonradiative energy transfer in the NPLs film is successfully suppressed. The nonstacked NPL‐LEDs with pure green emission of 521.5 nm exhibit a low turn‐on voltage of 2.1 V, a maximum luminance of 22 400 cd m −2 , a peak external quantum efficiency (EQE) of 2.16%, which is a sixfold enhancement comparing to the stacked NPL‐LED (EQE = 0.34%). This work demonstrates the potential of core/crown NPLs for ultrawide color gamut displays.