Patterning Technology of High-Resolution Quantum Dots
Significance The evolution of display technology is a cornerstone of modern technological advancement,fundamentally transforming how humans interact with machines.This transformation is vividly apparent in human-computer interactions,where the integration of sophisticated display technologies has led to more intuitive and immersive experiences.The global living standard improvement has further fueled expectations for advanced display devices,with consumers seeking higher quality,efficiency,and functionality.The advent of near-eye display technologies such as augmented reality(AR),mixed reality(MR),and virtual reality(VR)has only heightened the demands for high-resolution microdisplays.These emerging technologies require displays that provide not only high resolution but also compactness,energy efficiency,and the ability to reproduce colors accurately and vividly.The current market is dominated by micro-LED technology and recognized for its superior brightness and energy efficiency.However,the production of full-color micro-LEDs poses significant challenges,chiefly in the massive transfer of differently colored LED chips onto a single wafer.This process demands an exceptionally high yield rate,making it both technologically challenging and costly.As a new type of semiconductor nanocrystal materials with quantum confinement effects,quantum dots(QDs)have sparked great interest in the display field due to their unique properties such as tunable bandgaps,high quantum yields,high stability,and potential for cost-effective solution processing.QDs typically adopt a core-shell structure[Fig.1(a)]and by adjusting the energy levels of the core-shell structure,excitons within the QDs can be confined.Organic ligands on the surface of QD shells provide steric hindrance among the dots,thus preventing aggregation and fluorescence quenching.The physicochemical properties of QDs can be adjusted by changing their organic ligands.Since Alivisatos's research team first reported LEDs with QDs as the electroluminescent layer in 1994,QD display devices have undergone 30 years of research.Additionally,high-resolution display devices using QDs have been realized via various patterning technologies to exhibit excellent device performance and fine pixel patterns.Although high-resolution patterning technology based on QDs has been extensively studied,there is still a lack of comprehensive reviews and summaries of recent work.Therefore,it is significant to summarize existing research and explore future development trends.Progress The current leading high-resolution QD patterning technologies encompass inkjet printing,photolithography,photo-crosslinking,region-selective deposition,transfer printing,and in-situ fabrication.These technologies are thoroughly compared and summarized in their process flows,strengths,and weaknesses,as depicted in Figs.2,6,and 8-12.In 2023,the team led by researcher Chen Zhuo from BOE Technology Group Co.,Ltd.utilized electrospray inkjet printing for fabricating both bottom-emitting and top-emitting electroluminescent QD devices,achieving a resolution of 500 ppi.In 2020,the team of Xu Xiaoguang at BOE successfully created a 500 ppi full-color passive matrix QD light-emitting device by a sacrificial layer-assisted photolithography method.That same year,Moon Sung Kang and the team at Sogang University in the republic of Korea developed a method for patterning QDs with a photo-driven ligand crosslinking agent,successfully producing full-color QD patterns with a resolution of 1400 ppi.In 2021,Sun Xiaowei and the team at Southern University of Science and Technology achieved a large-area full-color QD thin film with 1000 ppi resolution via selective electrophoretic deposition.In 2019,Hu Binbin at Henan University reported on assembling QD nanoparticles into microstructures via wetting-induced deposition.In 2021,the team led by Chen Shuming at Southern University of Science and Technology built a resonant cavity in white light QD light-emitting devices to achieve full-color patterned QD devices and a QD film patterning resolution of 8465 ppi.In 2015,Taeghwan Hyeon and the team at the Institute for Basic Science in the republic of Korea realized QD light-emitting devices with a resolution of 2460 ppi using gravure transfer printing technology.In 2022,our team collaborated with the team of Qian Lei at the Ningbo Institute of Materials Technology and Engineering,Chinese Academy of Sciences,integrated transfer printing with Langmuir-Blodgett film technology to create ultra-high pixel density QD light-emitting devices at 25400 ppi.In 2021,Zhong Haizheng and the team at the Beijing Institute of Technology prepared patterned CsPbI3 QD patterns on substrates via laser direct writing in situ.Conclusions and Prospects As carriers of visual information,display devices play an indispensable role in our daily lives.Emerging as revolutionary materials,QDs have become the ideal choice for next-generation display technologies with their unique properties such as tunable bandgaps,high quantum yields,and stability.Consequently,mastering high-resolution QD patterning is a crucial challenge that should be addressed for QD display devices to make significant strides in the market.In summary,various high-resolution QD patterning technologies require further detailed exploration to advance the applications and development of QD light-emitting devices in high-quality displays.
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