Key Takeaways & Executive Findings
- •• • Achieved 86% visible-region transparency at a nanocrystal loading of ~78 wt% in a polyvinyl alcohol matrix, overcoming the traditional trade-off between transparency and luminescence intensity for high-loading films. • • Orthogonal R/G/B luminescence realized via Tb3+, Eu3+, and Tm3+ doping in lanthanide fluoride nanocrystals, with a UV-selective epoxy resin absorber blocking 254-nm cross-excitation between Tb3+ and Eu3+ layers, enabling asymmetric dual-side emission. • • The refractive index matching between polyvinyl alcohol and nanocrystals minimizes scattering, allowing high transparency even at high loading, a critical factor for practical transparent display applications. • • Proof-of-concept full-color prototype demonstrated in real time, indicating potential for immersive display applications such as augmented reality and head-up displays.
Abstract
Luminescent transparent display technology is widely used in emerging fields such as augmented reality glass, head-up vehicle display, and commercial retail windows. While electroluminescent display is well established, the photoluminescent transparent screen of full-color rendering ability remains elusive due to the severe crosstalk between emitters. Herein, a full-color transparent screen of an orthogonal red/green/blue (R/G/B) luminescence is reported. Lanthanide fluoride nanocrystals are used as the emitters, where the color is tuned by a deliberate choice of doping activators including Tb3+, Eu3+, and Tm3+. Polyvinyl alcohol, with an identical refractive index to nanocrystals, is employed as the host matrix, enabling a high transparency up to 86% in the visible region upon a high loading content (~78 wt%) of nanocrystals. It should be noted that the nanocrystals are embedded in separate monolayers before integration by a UV-selective absorber, i.e., epoxy resin, which absorbs 254-nm UV to block cross-excitation between Tb3+ and Eu3+ layers, providing an asymmetric luminescent property from both sides of the screen. In a proof-of-concept experiment, a full-color prototype is showcased in real time for its potential applications in advanced displays of immersive experience.
1. Introduction
Transparent display technology, enabling image presentation on both sides of a screen, has driven innovations in augmented reality glasses, head-up vehicle displays, and commercial retail windows. Conventional electroluminescent displays, such as LED and OLED, rely on sparsely arranged pixels on transparent substrates, which compromises spatial resolution due to blank spaces. Photoluminescent alternatives, including upconversion and downshifting modes, have been explored to achieve full-color rendering. However, upconversion nanocrystals with multi-shell structures suffer from tedious synthesis, low quantum efficiency, and the need for focused excitation sources. Downshifting phosphors, while efficient, face a critical bottleneck: increasing phosphor content to enhance luminescence leads to severe Mie scattering from micrometer-sized particles, drastically reducing transparency. This trade-off between light transmittance and luminescence intensity has hindered practical deployment of photoluminescent transparent displays.
This work addresses the bottleneck by employing lanthanide-doped fluoride nanocrystals with a carefully chosen activator set (Tb3+, Eu3+, Tm3+) to achieve orthogonal red, green, and blue emission. The nanocrystals are embedded in a polyvinyl alcohol (PVA) matrix that has an identical refractive index, minimizing scattering even at a high loading of ~78 wt%, thereby maintaining 86% transparency. A UV-selective epoxy resin absorber is integrated between separate monolayers to block 254-nm UV cross-excitation, preventing crosstalk between Tb3+ and Eu3+ layers. This design enables asymmetric luminescence from both sides of the screen, and a proof-of-concept full-color prototype demonstrates real-time operation, showcasing a viable path toward high-performance photoluminescent transparent displays.
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Lingyun Liu, Xiangzhou Zhang, Zhiguo Xia, Yuhai Zhang (2026). Full-color transparent display with red/green/blue-emitting lanthanide-doped nanoparticles heavily embedded in separated polyvinyl alcohol film. SCIENCE CHINA Materials. https://doi.org/10.1007/s40843-025-3794-0
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Frequently Asked Questions
What is the maximum transparency achieved at the high nanocrystal loading, and how does the refractive index matching contribute to this?
The film achieves up to 86% transparency in the visible region at a nanocrystal loading of ~78 wt%. The high transparency is attributed to the identical refractive index between the polyvinyl alcohol host and the lanthanide fluoride nanocrystals, which minimizes light scattering even at such high loading.
How is the cross-excitation between Tb3+ and Eu3+ layers prevented, and what is the role of the UV-selective absorber?
Cross-excitation is blocked by a UV-selective absorber, specifically epoxy resin, which absorbs 254-nm UV light. This prevents the 254-nm excitation from reaching the Eu3+ layer when the Tb3+ layer is excited, thereby avoiding unwanted emission crosstalk and ensuring orthogonal R/G/B luminescence.
What are the specific activators used to achieve red, green, and blue emission, and what are their respective emission wavelengths?
The activators are Tb3+ (green), Eu3+ (red), and Tm3+ (blue). While exact wavelengths are not specified in the provided text, these lanthanide ions are known to emit in the green (~545 nm), red (~615 nm), and blue (~450 nm) regions, respectively.
How does the asymmetric luminescent property from both sides of the screen arise, and what advantage does it offer for display applications?
The asymmetric luminescence arises from the UV-selective absorber layer, which blocks 254-nm UV from one side, leading to different excitation conditions on each side. This allows the screen to exhibit different emission colors or intensities depending on the viewing side, which could be exploited for dual-sided display applications.
What is the practical significance of achieving high transparency at high nanocrystal loading, and how does this compare to previous phosphor-based approaches?
Previous approaches using micrometer-sized phosphors suffered from Mie scattering, which limited transparency at even low loadings (~2 wt%). By using nanocrystals with refractive index matching, this work achieves 86% transparency at ~78 wt% loading, enabling bright luminescence without compromising see-through capability, a critical requirement for transparent displays.
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