Color Conversion of GaN-Based Micro Light-Emitting Diodes Using Quantum Dots

Lee, Ching-Ting; Cheng, Chih‐Chieh; Lee, Hsin-Ying; Chu, Ying-Chien; Fang, Yen-Hsiang; Chao, Chia-Hsin; Wu, Ming-Hsien

doi:10.1109/lpt.2015.2462072

Cited by 20 publications

(8 citation statements)

References 18 publications

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“…For achieving effectively higher path lengths in a given film thickness, two other approaches have also been used that are not analyzed here. The first is the use of built-in Bragg reflectors in the structure to make a microcavity in the QD-containing film [2], and the second is to add scattering particles that can increase the effective optical path length and therefore absorption [13].…”

Section: -5 / J Osinskimentioning

confidence: 99%

“…Numerous presentations and articles have proposed the use of quantum dots (QDs) as a downconverter material dispersed in thin organic films for applications in microLED displays and color filters [1][2][3] but without detail on the design requirements. In the case of microLEDs, this approach allows making a fullcolor RGB display from monochromatic blue GaN starting sources, thereby avoiding the challenges of massively parallel transfer from three separate types of LED wafers with three different performance characteristics.…”

Section: Introductionmentioning

confidence: 99%

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4‐5: Quantum Dot Design Criteria for Color Conversion in MicroLED Displays

Osinski

Palomaki²

2019

Symp Digest of Tech Papers

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Published absorption values of common types of colloidal quantum dots have been used to calculate the loading requirements in a thin polymer film for application in color- converted microLED displays. The loading requirements as a function of the QD material and design are explored and discussed, with the goal of maximizing blue photon absorption for conversion to red and green in a model layer 5 microns thick.

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Section: -5 / J Osinskimentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

4‐5: Quantum Dot Design Criteria for Color Conversion in MicroLED Displays

Osinski

Palomaki²

2019

Symp Digest of Tech Papers

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“…For QDs encapsulated in organic ligands and monodispersed in solutions such as toluene, octane, or hexane, a controlled ligand exchange process is necessary for multilayer coatings . This process is time-consuming, especially as relatively thick films are required for near-complete absorption from the highly efficient blue LED emitters, resulting in films that are not chemically robust for post-processing steps. − QDs dispersed in an optically transparent curable polymer would not only result in chemical stability of the QD film but also protect the QDs from degradation due to ambient oxidation. ,,− Finally, to prevent the gradual loss in color intensity and short QD lifetime due to exposure to high photon fluxes and heat from the LED source, remote color converters placed away from the base converter and held at room temperature are a great alternative to achieve high-purity color profiles with a longer life cycle. − …”

Section: Introductionmentioning

confidence: 99%

Freestanding High-Resolution Quantum Dot Color Converters with Small Pixel Sizes

Srivastava

Lee

Fitzgerald

et al. 2022

ACS Appl. Mater. Interfaces

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Designing the next generation of high-resolution displays requires high pixel density per area and small pixel sizes without compromising the optical quality. Quantum dots (QDs) have been demonstrated as a promising material system for down-conversion of blue emission as they provide pure colors on the wide color gamut. However, for high color-conversion efficiency, the required QD film thickness has not been compatible with small pixel sizes. In this work, we develop a new type of freestanding QD-based color converter for efficient optical down-conversion from inorganic blue light-emitting diodes (LEDs) in a color-by-blue configuration. CdSe/ZnS core–shell QDs in a UV-curable polymer matrix are encapsulated within cavities formed by patterning and bonding a pair of patterned quartz substrates. By controlling the required QD thickness and the pixel size independently, we demonstrate freestanding monochrome red and green converters with small pixel sizes down to 5 × 5 μm2 and a high resolution of >3600 ppi. The optical studies show that the QD film thickness required for efficient color conversion can be successfully realized even for the small pixel sizes. We further combine green and red pixels in a single converter to achieve white emission when combined with blue LED emission. The QD color converter design and processing are decoupled from the LED fabrication and can be easily scaled to wafer-size integration with arbitrary pixel sizes for QD-based RGB displays with ultrahigh resolution.

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“…Consequently, the color purity of red and green QDs/micro-LEDs would be not good. The distributed Bragg reflector (DBR) with high reflectivity in the blue light region was deposited on the QD color conversion layer to solve the problem of the non-absorbed blue light [8,9]. However, since the DBR reflectivity depends on the incident angle of the light, the DBR reflectivity will be reduced if the light is not incident perpendicularly into the DBR structure [10,11].…”

Section: Introductionmentioning

confidence: 99%

Improved Color Purity of Monolithic Full Color Micro-LEDs Using Distributed Bragg Reflector and Blue Light Absorption Material

et al. 2020

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In this study, CdSe/ZnS core-shell quantum dots (QDs) with various dimensions were used as the color conversion materials. QDs with dimensions of 3 nm and 5 nm were excited by gallium nitride (GaN)-based blue micro-light-emitting diodes (micro-LEDs) with a size of 30 μm × 30 μm to respectively form the green and red lights. The hybrid Bragg reflector (HBR) with high reflectivity at the regions of the blue, green, and red lights was fabricated on the bottom side of the micro-LEDs to reflect the downward light. This could enhance the intensity of the green and red lights for the green and red QDs/micro-LEDs to 11% and 10%. The distributed Bragg reflector (DBR) was fabricated on the QDs color conversion layers to reflect the non-absorbed blue light that was not absorbed by the QDs, which could increase the probability of the QDs excited by the reflected blue light. The blue light absorption material was deposited on the DBR to absorb the blue light that escaped from the DBR, which could enhance the color purity of the resulting green and red QDs/micro-LEDs to 90.9% and 90.3%, respectively.

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Color Conversion of GaN-Based Micro Light-Emitting Diodes Using Quantum Dots

Cited by 20 publications

References 18 publications

4‐5: Quantum Dot Design Criteria for Color Conversion in MicroLED Displays

4‐5: Quantum Dot Design Criteria for Color Conversion in MicroLED Displays

Freestanding High-Resolution Quantum Dot Color Converters with Small Pixel Sizes

Improved Color Purity of Monolithic Full Color Micro-LEDs Using Distributed Bragg Reflector and Blue Light Absorption Material

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