Color-stable highly luminescent sky-blue perovskite light-emitting diodes

Abstract

Perovskite light-emitting diodes (PeLEDs) have shown excellent performance in the green and near-infrared spectral regions, with high color purity, efficiency, and brightness. In order to shift the emission wavelength to the blue, compositional engineering (anion mixing) and quantum-confinement engineering (reduced-dimensionality) have been employed. Unfortunately, LED emission profiles shift with increasing driving voltages due to either phase separation or the coexistence of multiple crystal domains. Here we report color-stable sky-blue PeLEDs achieved by enhancing the phase monodispersity of quasi-2D perovskite thin films. We selected cation combinations that modulate the crystallization and layer thickness distribution of the domains. The perovskite films show a record photoluminescence quantum yield of 88% at 477 nm. The corresponding PeLEDs exhibit stable sky-blue emission under high operation voltages. A maximum luminance of 2480 cd m−2 at 490 nm is achieved, fully one order of magnitude higher than the previous record for quasi-2D blue PeLEDs.

The Dominant Energy Transport Pathway in Halide Perovskites: Photon Recycling or Carrier Diffusion?

“…Note that high internal PL QY (η IN ) is critical for intensive photon recycling. [61,62] The internal QY is expected to approach unity. [50] The reported external quantum yields are as high as 60-88%.…”

“…For solar cells, carrier diffusion and photon recycling imply different impacts on open-circuit voltage. For example, although much effort has been made, the state-of-the-art external quantum efficiencies (EQEs) of 2D perovskites based LEDs are only around 10%, [10,62,66] which are remarkably lower than EQE of CdSe-CdS core-shell quantum dots (20.5%). [20] Whereas, high diffusion coefficients may reduce V OC in the presence of nonradiative surface recombination.…”

Recent advances and prospects toward blue perovskite materials and light‐emitting diodes

“…They served as ligands to limit the further growth in the out‐of‐plane direction, as well as to prevent restacking between individual crystals. Octylammonium bromide (OCTABr), ethylammonium bromide (EABr), butylammonium bromide (BABr), and phenylethylammonium bromide (PEABr) have commonly been used as A‐site ligands to adjust the dimension. By reducing the number of inorganic layers (n), the bandgap of 2D perovskites can be tuned from 2.6 eV (n = 4) to 3.1 eV (n = 1; Figure A) …”

“…B, PL spectra of perovskite PEA 2 A 1.5 Pb 2.5 Br 8.5 with 0 to 60% IPABr additive. The inset is a photograph of the corresponding films under 365 nm UV irradiation . Copyright 2018, Springer Nature.…”

“…This result strongly demonstrates that EABr can control the transition of the perovskite phase from bulk to layer. Nevertheless, inefficient charge transfer can result in the dual emission of EL …”