An efficiency record in light-emitting diodes (LEDs) made of perovskite materials has been achieved by an international team that includes the research group of Professor Qihua Xiong at the School of Physical and Mathematical Sciences in Nanyang Technological University (NTU), Singapore.
A high-efficiency perovskite LED device.
Photo credit: K. Lin et al.
Writing in the October 2018 issue of the journal Nature, the team, which also includes researchers at Huaqiao University (China) and the University of Toronto (Canada), announced a new world record of 20 percent efficiency for light-emitting diodes (LEDs) made from halide perovskite materials.
Halide perovskites are a class of cheap and naturally abundant materials poised to take the place of traditional semiconductors in next-generation LEDs, solar cells, and other electronic devices. The new 20 percent efficiency record is significant because it means that, for the first time, the efficiency of perovskite LEDs is comparable to commercially-available conventional LEDs, organic LEDs, and quantum dot LEDs.
Conventional LEDs, made of semiconductor materials such as gallium arsenide, are in widespread use because of their high efficiency. This efficiency, defined as the proportion of electrical power successfully converted to light, ranges from 15 to 25 percent for commercial LEDs. By comparison, incandescent bulbs have only about 2 percent efficiency.
In recent years, however, scientists have begun looking into replacing traditional semiconductors with materials known as halide perovskites. One major appeal of perovskite-based devices is that they can be manufactured by methods such as inkjet-printing or spin coating, which are much cheaper than standard semiconductor fabrication techniques.
Prof. Qihua Xiong, one of the lead authors of the paper.
The researchers found that by mixing in a carefully-chosen additive during the manufacturing process, many defects in the all-inorganic perovskite atomic structure can be removed. Since these defects wastefully scatter the electric current flowing in the material, removing them results in a substantial jump in the light-emission efficiency. The team found an efficiency of over 20 percent, compared to the maximum efficiencies of 12 to 14 percent reported for earlier perovskite LEDs.
"Perovskite LEDs are much cheaper to make," explains Professor Xiong, one of the lead authors of the paper. "The fact that we achieved an efficiency comparable to commercial LEDs is very encouraging. It marks a step toward cheaper LEDs for use in lighting and display screens in the future."
This work has been featured in Nature News and Views.
K. Lin et al., Perovskite light-emitting diodes with external quantum efficiency exceeding 20 per cent, Nature 562, 245 (2018).