Efficient Blue Electroluminescence Using Quantum-Confined Two-Dimensional Perovskites

Abstract

Solution-processed hybrid organic-inorganic lead halide perovskites are emerging as one of the most promising candidates for low-cost light-emitting diodes (LEDs). However, due to a small exciton binding energy, it is not yet possible to achieve an efficient electroluminescence within the blue wavelength region at room temperature, as is necessary for full-spectrum light sources. Here, we demonstrate efficient blue LEDs based on the colloidal, quantum-confined 2D perovskites, with precisely controlled stacking down to one-unit-cell thickness (n = 1). A variety of low-k organic host compounds are used to disperse the 2D perovskites, effectively creating a matrix of the dielectric quantum wells, which significantly boosts the exciton binding energy by the dielectric confinement effect. Through the Förster resonance energy transfer, the excitons down-convert and recombine radiatively in the 2D perovskites. We report room-temperature pure green (n = 7-10), sky blue (n = 5), pure blue (n = 3), and deep blue (n = 1) electroluminescence, with record-high external quantum efficiencies in the green-to-blue wavelength region.

Advances in Quantum‐Confined Perovskite Nanocrystals for Optoelectronics

“…Recent Figures a-d) reproduced with permission. [53] Copyright 2016, American Chemical Society. e) Perovskite structures with different thicknesses (n = number of layers), showing the evolution of 2D (n = 1) to 3D (n = ∞).…”

“…As discussed before, blue emitting bromide-based perovskites can be prepared with higher PLQYs and stronger exciton binding energies than the bulk-like chloride variants, enabling more efficient blue as well as white light-emitting LEDs. [11,[53][54][55] For instance, Kumar et al have demonstrated the fabrication of blue LEDs using atomically thin halide perovskite nanoplatelets; and the electroluminescence can be tuned across the blue-green region by using hybrid perovskite nanoplatelets of different thickness (Figure 4a-d). [53] In this work, nanoplatelets were dispersed in a low dielectric constant (low-k) and wide bandgap organic semiconducting matrix to increase the exciton binding energy through the dielectric confinement effect (Figure 4b).…”

“…[11,[53][54][55] For instance, Kumar et al have demonstrated the fabrication of blue LEDs using atomically thin halide perovskite nanoplatelets; and the electroluminescence can be tuned across the blue-green region by using hybrid perovskite nanoplatelets of different thickness (Figure 4a-d). [53] In this work, nanoplatelets were dispersed in a low dielectric constant (low-k) and wide bandgap organic semiconducting matrix to increase the exciton binding energy through the dielectric confinement effect (Figure 4b). Moreover, the organic matrix facilitates the radiative recombination in nanoplatelets through Förster resonance energy transfer and thus enhances the efficiency of the LED.…”

Structure of Organometal Halide Perovskite Films as Determined with Grazing‐Incidence X‐Ray Scattering Methods

“…Thus, a range of low dimensional perovskites can easily be produced as depicted in Figure 4a. [59] Associated with the confinement in 2D perovskites, the optoelectronic properties of the material are also affected: [59][60][61] Figure 4a shows the absorbance (black) and photoluminescence spectra (red), which indicate a pronounced blue-shift for lower dimensional varieties due to quantum confinement, with absorption and emission behavior becoming more excitonic in nature. In the spectra of the mixed dimensional species, additional contributions from the lower dimensional variants are observed.…”

Emergence of Nanoplatelet Light-Emitting Diodes

“…However, when various nanocrystal CsPbX 3 have been utilized together as emitters in LEDs, the fast anion exchange can occur [151,152]. As a solution, 2D CsPbX 3 nanocrystals with precisely tunable thickness are promising to optoelectronic applications due to the merits, particularly for their quantum confinement effect [153,154]. Toward this end, Yang et al demonstrated that ultrathin CsPbBr 3 NPLs having precisely tunable dimensions could be achieved in a large scale via a simple one-pot method and could be utilized to be the emitting layer of blue LEDs [155].…”