LED

New Perovskite LEDs Set Record for Internal Luminescence

07 November 2018

Perovskite-based light-emitting diodes (LEDs) can compete with organic LEDs (OLEDs) in terms of efficiency, but need better stability for widespread use in consumer electronics. When perovskite LEDs were first developed, they had a lifetime of just a few seconds. New devices developed at the University of Cambridge, U.K., have a half-life close to 50 hours. While this is nowhere near the lifetime required for High-resolution transmission electron microscopy image (left) of a perovskite-polymer sample. Cross-sectional scanning electron microscopy image (right) of the LED structure. Source: University of CambridgeHigh-resolution transmission electron microscopy image (left) of a perovskite-polymer sample. Cross-sectional scanning electron microscopy image (right) of the LED structure. Source: University of Cambridgecommercial applications, it marks a big improvement over the course of four years.

Earlier versions of hybrid perovskite LEDs designed at the university suffered from defects in the crystal structure, resulting in non-emissive losses from the perovskite layer and limited light-emission efficiency. Improved light-emission, approaching 100% internal luminescence efficiency, was recently achieved by engineering a composite layer of the perovskites together with a polymer.

The LED emissive layer design comprises quasi-2D and 3D perovskites and an insulating polymer. Electric charge pairs migrate from the 2D to the 3D regions in one-trillionth of a second on exposure to an ultra-fast laser. The separated charges in the 3D regions, which are isolated from defects by the polymer, then recombine and emit light extremely efficiently.

The diodes exhibit external quantum efficiencies of up to 20.1%, a new record for perovskite LEDs.

To contact the author of this article, email shimmelstein@globalspec.com


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