A research team from Zhejiang University and University of Cambridge has reported the downscaling of LEDs based on perovskite semiconductors to below the conventional size limits. Micro- and nano-perovskite LEDs (micro-PeLEDs/nano-PeLEDs) with characteristic pixel lengths from hundreds of micrometres down to about 90 nm were demonstrated, through a localized contact fabrication scheme that prevents non-radiative losses at the pixel boundaries.
For these near-infrared (NIR) and green micro-PeLEDs, average external quantum efficiencies (EQEs) were maintained at around 20% across a wide range of pixel lengths (650 to 3.5 μm), exhibiting minimum performance reduction on downsizing.
The nano-PeLEDs with characteristic pixel lengths down to about 90 nm represent the smallest LEDs reported, enabling a record-high pixel density of 127,000 pixels per inch (PPI) among all classes of LED arrays.
It is possible to achieve ultrahigh-definition and ultrahigh-precision photoelectric displays by reducing the size of LEDs, according to Zhao Baodan from Zhejiang University. However, due to the complex process technology, the manufacturing cost of micro-LEDs is extremely high. Moreover, when the pixel size is reduced to about 10 micrometers or less, the efficiency of micro-LEDs will drop sharply. This is precisely the pixel size needed for ultrahigh-resolution applications in high-end augmented reality (AR) and virtual reality (VR). Therefore, the high cost and low light-emitting efficiency have restricted the large-scale commercial application of micro-LEDs.
After the team first introduced the concept of "micro-perovskite LEDs" in 2021, they have effectively ensured the light-emitting efficiency of LEDs through a series of material and process innovations. As a result, they are able to manufacture perovskite LEDs with pixel sizes ranging from hundreds of micrometers to 90 nanometers. Moreover, while downscaling, they have maintained excellent performance.
The researchers noted that traditional micro-LEDs experience a sharp decline in efficiency once their size falls below 10 micrometers. In contrast, the micro- and nano-perovskite LEDs only begin to show downscaling effects at an extremely small size of about 180 nanometers, demonstrating significant advantages.
To realize practical display applications, the LED arrays must be driven by programmable circuits to deliver useful information, which requires further cooperation with the industry. The team is currently actively promoting its application.
