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Overcoming the electroluminescence efficiency limitations of perovskite light-emitting diodes

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Science  04 Dec 2015:
Vol. 350, Issue 6265, pp. 1222-1225
DOI: 10.1126/science.aad1818

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Brighter perovskite LEDs

Organic-inorganic hybrid perovskites such as methyl ammonium lead halides are attractive as low-cost light-emitting diode (LED) emitters. This is because, unlike many inorganic nanomaterials, they have very high color purity. Cho et al. made two modifications to address the main drawback of these materials, their low luminescent efficiency. They created nanograin materials lacking free metallic lead, which helped to confine excitons and avoid their quenching. The perovskite LEDs had a current efficiency similar to that of phosphorescent organic LEDs.

Science, this issue p. 1222

Abstract

Organic-inorganic hybrid perovskites are emerging low-cost emitters with very high color purity, but their low luminescent efficiency is a critical drawback. We boosted the current efficiency (CE) of perovskite light-emitting diodes with a simple bilayer structure to 42.9 candela per ampere, similar to the CE of phosphorescent organic light-emitting diodes, with two modifications: We prevented the formation of metallic lead (Pb) atoms that cause strong exciton quenching through a small increase in methylammonium bromide (MABr) molar proportion, and we spatially confined the exciton in uniform MAPbBr3 nanograins (average diameter = 99.7 nanometers) formed by a nanocrystal pinning process and concomitant reduction of exciton diffusion length to 67 nanometers. These changes caused substantial increases in steady-state photoluminescence intensity and efficiency of MAPbBr3 nanograin layers.

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