Perovskite-based LEDs boast near 100% internal quantum efficiencies

November 16, 2018 //By Julien Happich
Perovskite-based LEDs boast near 100% internal quantum efficiencies
Designing a LED with emissive layers comprising quasi-two-dimensional and three-dimensional (2D/3D) perovskites and an insulating polymer, researchers from Cambridge University have set a new efficiency record for perovskite-based LEDs.

The perovskite–polymer bulk heterostructure light-emitting diodes described in a paper titled "High-efficiency perovskite–polymer bulk heterostructure light-emitting diodes" and published in Nature Photonics is reported to achieve light-emission efficiencies close to the theoretical efficiency limit of thin-film OLEDs. Because non-radiative recombination pathways are effectively eliminated in this structure, the perovskite-polymer bulk heterostructure LEDs exhibited external quantum efficiencies of up to 20.1 percent (at current densities of 0.1 to 1mA cm−2).

What the researchers observed was that when shining an ultrafast laser on the structures, pairs of electric charges moved from the 2D regions to the 3D regions within 1ps, significantly faster than previous layered perovskite structures used in LEDs. The separate charges in the 3D regions then recombined to emit light at high efficiency.
“Since the energy migration from 2D regions to 3D regions happens so quickly, and the charges in the 3D regions are isolated from the defects by the polymer, these mechanisms prevent the defects from getting involved, thereby preventing energy loss,” explained researcher Dawei Di.
The researchers engineered the perovskite layer in the LEDs to show close to 100 percent internal luminescence efficiency. The perovskite materials were the same as those used to make highly efficient solar cells.

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