LEDs Cross A Major Performance Barrier Thanks To New Design

Two papers on LED research, shared in Nature, have reported a possible new family of LEDs, based on semiconductors known as Perovskite, have surpassed existing performance barriers. Improved designs for Perovskite LEDs (PLEDs) developed by Cao & his colleagues and Lin and his colleagues have both managed to break important technological barriers: the external quantum efficiency (EQE) of the devices, which quantifies the number of photons produced per electron consumed, by crossing an EQE of  20%.

These two groups have produced independently, two Perosvskitebased designs with significantly improved efficiency. Both designs have some similarities. Both designs consist of a  200nm perovskite layer, enclosed by electrodes modified to ensure that electrons and holes (quasiparticles formed by the absence of electrons in atomic lattices) are efficiently pumped into the perovskite. Like in all LEDs, when these electrons and holes combine, they release energy in the form of photons which escapes as light from the LED.

Similarly, both groups prepared perovskite layers using solutions, from which the semiconductors were crystallized to form the emissive components of the LEDs.

The first group, Cao and his colleagues, have designed a PLED using submicrometre-sized crystals of Perovskite sandwiched between a gold electrode and a transparent electrode but separated from the gold electrode by a thin layer of an organic material. This design increases the amount of light that escapes from the LED.

The 2nd group, Lin and his colleagues, made PLEDs based on a different perovskite and where the semiconductor device is sandwiched between an organic compound and an aluminum electrode. This design optimizes the efficiency with which charges that are pumped into the perovskite are converted into photons.

According to Nature:

Remarkably, the efficiencies with which the perovskite LEDs (PLEDs) produce light from electrons already rival those of the best-performing OLEDs, and have been achieved in less than four years since the report of the first PLED — suggesting that there is plenty of room for even further improvement in their performance.

The PLEDs,  have achieved efficiencies at par with existing Organic LEDs less than four years after the report on the first LED and therefore suggest there is room for even further improvement.