Efficient Blue Electroluminescence Using Quantum-Confined Two- Dimensional Perovskites

S Kumar and J Jagielski and S Yakunin and P Rice and YC Chiu and MC Wang and G Nedelcu and Y Kim and SC Lin and EJG Santos and MV Kovalenko and CJ Shih, ACS NANO, 10, 9720-9729 (2016).

DOI: 10.1021/acsnano.6b05775

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 Forster 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.

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