Multilayer Transfer Printing for Pixelated, Multicolor Quantum Dot Light-Emitting Diodes
journal contributionposted on 14.04.2016, 00:00 authored by Bong Hoon Kim, Sooji Nam, Nuri Oh, Seong-Yong Cho, Ki Jun Yu, Chi Hwan Lee, Jieqian Zhang, Kishori Deshpande, Peter Trefonas, Jae-Hwan Kim, Jungyup Lee, Jae Ho Shin, Yongjoon Yu, Jong Bin Lim, Sang M. Won, Youn Kyoung Cho, Nam Heon Kim, Kyung Jin Seo, Heenam Lee, Tae-il Kim, Moonsub Shim, John A. Rogers
Here, we report multilayer stacking of films of quantum dots (QDs) for the purpose of tailoring the energy band alignment between charge transport layers and light emitting layers of different color in quantum dot light-emitting diodes (QD LED) for maximum efficiency in full color operation. The performance of QD LEDs formed by transfer printing compares favorably to that of conventional devices fabricated by spin-casting. Results indicate that zinc oxide (ZnO) and titanium dioxide (TiO2) can serve effectively as electron transport layers (ETLs) for red and green/blue QD LEDs, respectively. Optimized selections for each QD layer can be assembled at high yields by transfer printing with sacrificial fluoropolymer thin films to provide low energy surfaces for release, thereby allowing shared common layers for hole injection (HIL) and hole transport (HTL), along with customized ETLs. This strategy allows cointegration of devices with heterogeneous energy band diagrams, in a parallelized scheme that offers potential for high throughput and practical use.