39‐4: <i>Invited Paper</i>: Innovation in Heavy Metal‐Free Quantum Dot Technology

Herein, emerging applications of luminescent semiconductor nanocrystals are addressed, such as quantum dots and quantum rods as down‐conversion materials used in liquid crystal displays (LCD). Their precisely tunable emission wavelengths and narrow emission bandwidths offer high color purity resulting in a wide color gamut with vivid colors for LCDs. Anisotropic materials, such as quantum rods, have the additional advantage of polarized emission, which can bring a significant improvement to the efficiency of LCD displays. The basic optical properties of these nanomaterials are considered, with a focus on quantum rods, and the challenges and progress in their assembly are discussed. Different techniques for quantum rod alignment are introduced such as shear‐oriented, electric field and magnetic field assisted assembly, mechanical rubbing, stretching, and electrospinning. The photoalignment approach allows for an easy arrangement of quantum rods in‐plane, and the implications of this method to patterning are considered. Different configurations of LCDs utilizing semiconductor quantum dots and quantum rods as down‐conversion layers are also presented, and the potential applications that are enabled by the wide range of emerging materials are highlighted.

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Luminescent Down‐Conversion Semiconductor Quantum Dots and Aligned Quantum Rods for Liquid Crystal Displays

Srivastava

Zhang

Schneider

et al. 2019

Advanced Science

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Semiconductor nanomaterial-based polarized light emission: From materials to light emitting diodes

Fang

Zhang

et al. 2023

Sci. China Mater.

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The overall optical efficiency of backlight-based liquid crystal displays (LCDs) is less than 5% due to the loss of backlight source by polarizers, color filter, liquid crystal layer and so on. Self-emissive light emitting diodes (LEDs) have been undergoing huge development due to their substantial market potentials to meet the demand of future display. More importantly, the polarized LEDs could enhance the energy utilization efficiency by avoiding light loss caused by polarizers. Therefore, it is desirable to look for effective methods to assemble high-quality anisotropic nanomaterial films so as to fabricate polarized LEDs with high degree of polarization and external quantum efficiency. Here, the photoelectrical properties of some semiconductor nanomaterials and their potential applications for polarized LEDs are introduced. The research progress in the field of polarized light emission from materials to films and then to LEDs is reviewed. Mechanisms of polarized emission, and different assembly strategies for polarized light emitting films and LEDs are also summarized and compared. Finally, several current challenges are discussed, and perspectives on future potential commercial application of polarized LEDs are offered. We hope this review will provide a valuable summary on current status and stimulate some new insightful ideas for future development of polarized LEDs.

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Progress toward blue-emitting (460–475 nm) nanomaterials in display applications

2021

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Recently, quantum dots (QD) and quantum rods (QRs) have become extremely popular in displays and lighting applications. Liquid crystal displays (LCDs) equipped with quantum dot enhancement films (QDEFs) offer extended color saturation, increasing said saturation from 60 to 70% to more than 100% of the NTSC color gamut. A plethora of research dealing with EL/PL properties and the device-based performance of these materials has been published. The tunable emission wavelength and the narrow emission bandwidth are the key features of quantum dots and perovskite nanoparticles that primarily depend on the nanoparticle size and material composition. QRs, in contrast, have a core–shell structure and emit polarized light that can roughly double the efficiency of modern displays. However, blue emission for QRs, because of the large bathochromic redshift during shell growth, is a serious problem. Besides photoluminescence, electroluminescence is also important for display applications. These QD-LEDs show a lower turn ON voltage in comparison to organic LEDs, which is very important for high-resolution displays. The solution-processed narrower emission QD-LEDs have already achieved efficiency and a brightness comparable to vacuum-deposited phosphorescent organic LEDs (OLEDs). However, the blue-emitting nanoparticles and their short operational lifetime are the key obstacles in the progression of these devices. Furthermore, recently the display and lighting industry are trying to reduce the short-wavelength emissions, particularly in the spectral region below 455 nm, which has a much greater impact on human ocular health and circadian rhythm. Thus, industries are aiming at blue light in the spectral range of 460–475 nm. This spectral range is very challenging for nanomaterials because of the limited choice of materials. In this review, we summarize the recent progress made in the blue-emitting nanomaterials with a different morphology and composition. This includes recent developments in low Cd materials. Both the PL and EL properties of these materials have been discussed depending on the NP’s shape and material composition. This review also aims to discuss the various device architectures employing blue-emitting NPs, any recent achievements and future challenges.

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39‐4: Invited Paper: Innovation in Heavy Metal‐Free Quantum Dot Technology

Cited by 3 publications

References 7 publications

Luminescent Down‐Conversion Semiconductor Quantum Dots and Aligned Quantum Rods for Liquid Crystal Displays

Luminescent Down‐Conversion Semiconductor Quantum Dots and Aligned Quantum Rods for Liquid Crystal Displays

Semiconductor nanomaterial-based polarized light emission: From materials to light emitting diodes

Progress toward blue-emitting (460–475 nm) nanomaterials in display applications

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