Identifying and Reducing Interfacial Losses to Enhance Color-Pure Electroluminescence in Blue-Emitting Perovskite Nanoplatelet Light-Emitting Diodes

Perovskite
nanoplatelets (NPls) hold promise for light-emitting
applications, having achieved photoluminescence quantum efficiencies
approaching unity in the blue wavelength range, where other metal-halide
perovskites have typically been ineffective. However, the external
quantum efficiencies (EQEs) of blue-emitting NPl light-emitting diodes
(LEDs) have reached only 0.12%. In this work, we show that NPl LEDs
are primarily limited by a poor electronic interface between the emitter
and hole injector. We show that the NPls have remarkably deep ionization
potentials (≥6.5 eV), leading to large barriers for hole injection,
as well as substantial nonradiative decay at the NPl/hole-injector
interface. We find that an effective way to reduce these nonradiative
losses is by using poly­(triarylamine) interlayers, which lead to an
increase in the  EQE of the blue (464 nm emission wavelength) and
sky-blue (489 nm emission wavelength) LEDs to 0.3% and 0.55%, respectively.
Our work also identifies the key challenges for further efficiency
increases.