The manufacturing of these perovskite LEDs is currently based on dipping or covering the targeted surface with liquid chemicals, a process which the researchers claim is difficult to setup, limited to small areas and with low consistency between samples.
To overcome this issue, the researchers assembled the perovskite LED by chemical vapour deposition (CVD).
"Chemical vapour deposition is already compatible with the industry, so in principle it would be easy to use this technology to produce LEDs," commented Professor Yabing Qi.
"The second advantage in using CVD is a much lower variation from batch to batch compared to liquid-based techniques. Finally, the last point is scalability: CVD can achieve a uniform surface over very large areas".
The chemicals required for the perovskite layer – lead bromide and methylammonium bromide – are bound to an indium tin oxide glass sheet and a polymer layer using CVD, in which the sample is exposed to gasses to convert the chemicals to perovskite.
Then the deposition of two additional layers and a gold electrode form the complete LED structure. The LED can form specific patterns using lithography during the manufacturing process.
"With large grains, the surface of the LED is rough and less efficient in emitting light. The smaller the grain size, the higher the efficiency and the brighter the light," explained Dr Lingqiang Meng. "By changing the assembly temperature, we can now control the growth process and the size of the grains for the best efficiency".
According to the team, the luminance currently reaches 560cd/m2.
