Nature Photonics - Stable and efficient quantum-dot light-emitting diodes based on solution-processed multilayer structures
Multilayer, colloidal quantum-dot based light-emitting diodes that exhibit high brightness, solution processability, colour tunability and narrow emission bandwidth are reported. These devices consist of a quantum-dot emissive layer sandwiched between an organic hole transport layer and an electron transport layer of ZnO nanoparticles, all of which are deposited using a solution process. The devices have maximum luminance and power efficiency values of 4,200 cd m^−2 and 0.17 lm W^−1 for blue emission, 68,000 cd m^−2 and 8.2 lm W^−1 for green, and 31,000 cd m^−2 and 3.8 lm W^−1 for orange-red. Moreover, with the incorporation of the ZnO nanoparticles, these devices exhibit high environmental stability, and the unencapsulated devices have operating lifetimes exceeding 250 h in low vacuum with an initial brightness of 600 cd m^−2.
According to the Nature Photonics article, UF researchers overcame this obstacle with a patented device structure that allows for depositing all the particles and molecules needed onto the LED entirely with spin-coating. Such a device structure also yields significantly improved device efficiency and lifetime compared to previously reported QD-based LED devices.
Spin-coating may not be the final manufacturing solution, however.
“In terms of actual product manufacturing, there are many other high through-put, continuous “roll-to-roll” printing or coating processes that we could use to fabricate large area displays or lighting devices,” Xue said. “That will remain as a future research and development topic for the university and a start-up company, NanoPhotonica, that has licensed the technology and is in the midst of a technology development program to capitalize on the manufacturing breakthrough.”
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