Using perovskite to make LED pixels as small as a virus

A team of physicists, engineers, opticians and photonics specialists at Zhejiang University, in China, working with a pair of colleagues from the University of Cambridge, in the U.K., has found a way to make pixels smaller by using perovskite. In their paper published in the journal Nature, the group describes how they used the mineral to create pixels as small as a virus.

As the research team notes, the rallying cry for electronics in the modern age is to add more technology to ever smaller base units. For computers, for many years, the goal was to double the number of transistors on a single integrated circuit. Similarly, reducing the size of pixels in video displays has led to sharper and sharper imagery.

The current standard for digital display technology is micro-LED, which is based on II-V semiconductors. Unfortunately, such technology becomes too expensive and inefficient to make pixels any smaller than the size currently in use. This led the team to wonder if a different base material might allow the creation of smaller pixels that would be both cost-effective and efficient. They turned to perovskite, the same mineral that is currently being investigated as a replacement for silicon in solar cells as a way to reduce costs.

The work involved creating semiconductors from perovskite that could be used as pixels on a display screen, which emit light when electricity is applied. The team found that test LEDs shone as bright as traditional LEDs without any loss in efficiency.

Inspired by their results, they made a smaller one, and found it also shone as bright as a traditional LED, but its cost did not grow and it remained as efficient as the larger test LED. They continued to make smaller and smaller LEDs until they made one that was just 90 nanometers wide, roughly the size of a virus. This translates to a record-high pixel density of 127,000 pixels per inch.

The LEDs made by the researchers thus far are all monochrome, which means the team will need to do more work to find out if color perovskite LEDs can truly outcompete those now in use. Also, it is not yet known how long such LEDs would last in real-world devices.

The team also acknowledges that there is a point of no return on reducing LED size, the human eye is only capable of discerning sharpness to a certain degree. Still, they suggest extremely tiny LEDs may find a home in such products as super-high-resolution augmented reality devices.

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