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A composite photoalignment layer for aligning liquid crystal molecules includes: a monomeric material; a photoinitiator or a thermal initiator; and an azo dye material. A method for preparing a composite photoalignment layer for aligning liquid crystal molecules includes: mixing, in solution form, a monomeric material, a photoinitiator or a thermal initiator, and an azo dye material; coating the mixed solution onto a substrate to form a thin film; exposing the thin film to polarized light; and, with a thermal initiator, heating the thin film to polymerize the monomeric material and form a solid thin film.

Air-flow sensing is essential in broad applications of weather forecasting, ocean monitoring, gas leakage alarming, and health monitoring. However, in severe environments where electrical power supply and cable connection are not available, the sensing of air flow in a self-powered way is a challenging issue. In this work, we reported a tribo-induced smart reflector to achieve the self-powered wireless sensing of the air flow by combining an aerodynamics-driven triboelectric nanogenerator (TENG) and a silver-coated polymer network liquid crystal. Upon being driven by the air flow, the developed reflector performed specular and diffused reflectance without and with charging by the TENG, respectively, enabling wireless sensing through mechanical–electrical–optical signal conversion. In the developed sensing paradigm, the sensing module can be fully self-powered without the need of signal pre-amplification, which is electrically separated from the light source and detection modules without cable connections. The applications of self-powered wireless wind speed sensing and breath monitoring were performed to demonstrate the effectiveness of the developed paradigm toward self-powered wireless sensing nodes in the internet of things.

Fiber-optic sensors have been developed to monitor the structural vibration with advantages of high sensitivity, immunity to electromagnetic interference (EMI), flexibility, and capability to achieve multiplexed or distributed sensing. However, the current fiber-optic sensors require precisely polarized coherent lasers as the lighting sources, which are expensive in cost and suffer from the power supply issues while operating at outdoor environments. This work aims at solving these issues, through developing a fully self-powered, natural-light-enabled approach. To achieve that, a spring oscillator-based triboelectric nanogenerator (TENG), a polymer network liquid crystal (PNLC), and an optical fiber were integrated. The external vibration drove the PNLC to switch its transparency, allowing the variation of the incident natural light in the optical fiber. Compared with the majority of conventional TENG-based active vibration sensors, the developed paradigm does not suffer from the EMI, without requirements of the signal preamplification which consumes additional energy. The vibration displacement monitoring was performed to validate the sensing effectiveness of the developed paradigm.

A composite photoalignment layer for aligning liquid crystal molecules includes: a monomeric material; a photoinitiator or a them叫initiator; and an azo dye material. A method for preparing a composite photoalignment layer for aligning liquid crystal molecules includes: mixing, in solution form, a monomeric material, a photoinitiator or a thermal initiator, and an azo dye material; coating the mixed solution onto a substrate to form a thin film; exposing the thin film to polarized light; and, with a thermal initiator, heating the thin film to polymerize the monomeric material and form a solid thin film.

Display technology has gradually but profoundly shaped the lifestyle of human beings. Liquid crystal display (LCD) and organic light-emitting diode (OLED) display are two mainstream displays in the market due to their high-quality performance, which are further being developed to be an ultra-thin, transparent, flexible and even foldable display. An alignment film is an indispensable part in LCDs as well as recently emerging transparent display, and deeply influence their contrast ratio (CR) and light efficiency. Alignment thin film used for LC molecules orientation should be characterized by high aligning order, non-contaminated film and robust photo-tolerance. The employment of an ultra-thin polarizing film is also significant in rigid or flexible OLED display to suppress the reflection from cathode layer so as to improve the CR and outdoor readability. Therefore, development on high-performance thin films either for LC alignment or flexible OLED display are highly demanded. Firstly, polyimide (PI) is a dominating material for LC alignment and is widely used in display devices, one of which is smart window. In general, smart windows are developed either by optimizing the scattering composites or by designing an appropriate electrode pattern, while little investigation has been carried out on the alignment layer. Here, an inhomogeneous vertical alignment thin film with micro-domain structure was proposed and employed on a normally transparent smart window. This inhomogeneity morphology on the thin film can considerably enhance the power-on haziness while provide an ultra-transparent power-off state. In addition, the performance on off-axis viewing, response speed and power consumption are much better than commercialized polymer-dispersed liquid crystal (PDLC) smart window. The proposed smart window can serve as color transparent display using edge-light wave-guiding. In addition to employing vertical polyimide thin film, we can use photoalignment material, azo-dye S

The authors of article number 1901824, published in volume 8, issue 7 (April 2020) of Advanced Optical Materials, regret that they missed the contribution from Valery V. Vashchenko and Olena V. Vashchenko. Both, Dr. V. V. Vashchenko and Dr. O. V. Vashchenko are from the State Key Lab of Advanced Displays and Optoelectronics Technologies, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong. They contributed to this work by proposing the idea of making broadband AD-1 material which was used as the dichromic dye in our device. This correction provides an updated author information. All of the authors confirm that they agree with the authorship of Dr. Valery V. Vashchenko and Dr. Olena V. Vashchenko.

Self-powered smart windows are desirable with the expectations of their energy-saving, weather-independent, user-controllable, and miniature performance. Recently developed solar- or thermal-powered smart windows largely depend on the weather conditions and have an extremely slow response, and only a certain portion of the saved energy can be utilized by the external circuit for mode conversion. In this work, a self-powered normally transparent smart window was developed by the conjunction of a rotary freestanding sliding triboelectric nanogenerator (RFS-TENG) and a polymer network liquid crystal (PNLC) cell. To fabricate the PNLC cell, the alignment layer with randomly distributed microdomains was constructed to encapsulate a mixture of LC polymers and nematic LCs. The opacity of the smart window exposed to an alternating electric field was considerably improved owing to the embedded microdomains and a dense web of LC polymers. The ultrahigh haziness greatly alleviates the charge density required for the LC actuation and thus enables the driving by the TENG where the charge amount is usually limited. The RFS-TENG was elaborately designed with six periodic bent triboelectric films and Ag electrodes, which presented an ultralow friction wear and met the frequency requirement to achieve the steady opacity. By harvesting the mechanical energies from ambient environments, the tribo-induced smart window can benefit a wide variety of fields, such as self-powered sunroofs, wind-driven smart farming systems etc. Copyright © 2020 American Chemical Society.

Polarization emission from halide perovskite is expected to bring a lot of benefits for next-generation displays, such as cost down, wide color gamut, and structure simplification. In this work, strong linearly polarized luminescence from emissive halide perovskites modulated by photoaligned azobenzene dye AD1 is demonstrated. The azobenzene dye functionalized halide perovskite thin films not only exhibit exceptionally high degree of polarization (DOP) of 86.2–93.1% for red, green, and blue emission, but also promise an improved environmental stability originating from the hydrophobic nature of the azobenzene dye. When these perovskite/AD1 composite films are applied in liquid crystal display panels to replace the conventional thick polarizer, the energy efficiency can be doubled and the color gamut can be extended to >120% NTSC. Furthermore, the AD1 functionalized strategy is successfully employed to generate linearly polarized electroluminescence from an inverted perovskite light-emitting diode, showing a high DOP of 47%. © 2020 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

In this article, we present a high performance smart window via micro‐domains manipulation on the alignment surface, which dramatically enhances the power‐on haze by 48%. Large‐scale window with ultra‐hazy state switching in less than 3.5 ms is demonstrated.

We propose here a novel multi-layered waveguide liquid crystal (LC) smart window with full color rendering based on a polymer-network liquid crystal system. The inserted position of three-primary-color LED light bars is specially designed, which is parallel to the LC alignment to obtain a higher difference between transparent and scattering states. The optimal matching of polymer-network LC system is experimentally achieved by comparing several groups of LC and reactive mesogen materials. The prepared smart window is measured and analyzed in detail including optical/chromatic test, morphology characterization, and actual application effect. The proposed architecture opens up new prospects of flexible color switchable ability and synchronized full-color display for smart windows without limitations of slow LC response time and complicated field sequential driving scheme.

The Polymer Network Liquid Crystal (PNLC) cell we fabricated is operating in a reverse mode of voltage‐off transparent state. It is found that when we apply voltage to the PNLC cells, the transmitted light color changed gradually and finally became a bit blue. This effect is not found in Polymer Dispersed LC (PDLC) window. The wavelength dependent transmittance voltage curves are reported and we will try to explain this effect by applying the anomalous diffraction theory.

The Polymer Network Liquid Crystal (PNLC) cell we fabricated is operating in a reverse mode of voltage‐off transparent state. It is found that when we apply voltage to the PNLC cells, the transmitted light color changed gradually and finally became a bit blue. This effect is not found in Polymer Dispersed LC (PDLC) window. The wavelength dependent transmittance voltage curves are reported and we will try to explain this effect by applying the anomalous diffraction theory.

In this article, we present a high performance smart window via micro‐domains manipulation on the alignment surface, which dramatically enhances the power‐on haze by 48%. Large‐scale window with ultra‐hazy state switching in less than 3.5 ms is demonstrated.

A front polarizer-free optically rewritable (ORW) liquid crystal displays (LCDs) has been made via a hybrid alignment configuration with dye-doped LCs. The hybrid structure consists of one optically active planar and one optically passive homeotropic alignment layer. The rewritability of the device is achieved by photo- reorienting the azo dye molecules in the active planar alignment layer. The dye doped in LCs function as a polarizer by following the LCs alignment via a guest-host effect so that the front polarizer can be eliminated. This makes the device more compact and easier to operate for image erasing and rewriting. The image rewriting time only requires ~9.0s, which is determined by the exposure energy and LC parameters. The hybrid-mode dye-doped optically rewritable (DDORW) LCD devices could find applications in E-paper, transparent display and various photonics devices.

In this article, two different azo dye stabilization methods were demonstrated. One is realized by two-step exposure while the other is simplified one-shot irradiation on a thin film. Various stabilization methods provide more flexibility on alignment layer preparation. Both methods offer an alignment layer with highly acceptable thermal and photo-stability. © 2018 International Display Workshops. All rights reserved.

Smart windows are attractive because of their numerous advantages such as elegance in construction design and energy conservation. Smart windows with variable transmission are especially desirable for obvious reasons. The simplest way to make a variable transmission smart window is to use two patterned polarizers, and control the transmission by changing the relative position of the two polarizers. We have demonstrated a high-dichroic-ratio polarizer by photoalignment and proposed a simple one-step photo-copy method to realize a continuous axis varying polarizer. The patterned polarizer shows high optical performance, and its thickness is as thin as 100 nm, which is favorable in practical window applications.

The ability to continuously alter the light transmittance through a window is significant for many optoelectronic devices. However, such versatility usually comes with additional unwanted power consumption. Here, we demonstrate transmittance-Tunable glass that operates without electrical power. The key element to the device is an axis-varying polarizer, which combines a photoalignment technique with dichroic dye self-Assembly mechanism. By linear translation of one patterned polarizer with respect to the other, different transmittance states can be achieved. Large-scale uniformity and relatively wide viewing angles (±60°) are also demonstrated. Furthermore, low-Temperature treatment (i.e., T < 80 °C) during fabrication demonstrates the device's potential to be made on the plastic substrate. The polarizer with patterned absorption axis can also be used as other optical components such as light amplitude shaping device. © 1989-2012 IEEE.

Broadband quarter wave plates are widely used in optical system, especially in display system. Above all, a broadband quarter wave plate can be treated as an isolator in display to provide “perfect” dark state so as to improve the contrast ratio. A kind of broadband quarter wave plate combined by two waveplates with angle deviated is proposed and manufactured in this paper using coating technique. Two methods of combination of the two waveplate are proposed and tried. The reflection spectrum shows that this kind of structure can provide good dark state in display system.

We employed the technique of photoalignment to fabricate polarizers using dichroic dyes and liquid crystal polymers. By varying the polarization direction of the UV/blue light, polarizers with spatially varying absorption axis were made. Such polarizers have many applications. As an example, we showed how mechanical translation of two such polarizers can be used as a variable transmission smart window, in which no electric power is needed. In this work, a 5cm x 5cm window device was made and demonstrated with very good bright and dark states.

A liquid crystal Pancharatnam-Berry (PB) axilens is proposed and fabricated via a digital micro-mirror-device-based photo-patterning system. The polarization-dependent device behaves as an axilens for a left-handed circularly polarized incident beam, for which an optical ring is focused with a long focal depth in the transverse direction at the output, and an anti-axilens for a right-handed circularly polarized incident beam, for which an optical ring gradually expands at the output. The modification of the size and the sharpness of the diffracted ring beam is demonstrated by encoding a positive (negative) PB lens term into the director expression of a PB (anti-)axicon.

Smart windows are attractive because of their numerous advantages such as elegance in construction design and energy conservation. Smart windows with variable transmission are especially desirable for obvious reasons. The simplest way to make a variable transmission smart window is to use two patterned polarizers, and control the transmission by changing the relative position of the two polarizers. We have demonstrated a high-dichroic-ratio polarizer by photoalignment and proposed a simple one-step photo-copy method to realize a continuous axis varying polarizer. The patterned polarizer shows high optical performance, and its thickness is as thin as 100 nm, which is favorable in practical window applications.

A front polarizer-free optically rewritable (ORW) liquid crystal displays (LCDs) has been made via a hybrid alignment configuration with dye-doped LCs. The hybrid structure consists of one optically active planar and one optically passive homeotropic alignment layer. The rewritability of the device is achieved by photo- reorienting the azo dye molecules in the active planar alignment layer. The dye doped in LCs function as a polarizer by following the LCs alignment via a guest-host effect so that the front polarizer can be eliminated. This makes the device more compact and easier to operate for image erasing and rewriting. The image rewriting time only requires ~9.0s, which is determined by the exposure energy and LC parameters. The hybrid-mode dye-doped optically rewritable (DDORW) LCD devices could find applications in E-paper, transparent display and various photonics devices.

We employed the technique of photoalignment to fabricate polarizers using dichroic dyes and liquid crystal polymers. By varying the polarization direction of the UV/blue light, polarizers with spatially varying absorption axis were made. Such polarizers have many applications. As an example, we showed how mechanical translation of two such polarizers can be used as a variable transmission smart window, in which no electric power is needed. In this work, a 5cm x 5cm window device was made and demonstrated with very good bright and dark states.

The ability to continuously alter the light transmittance through a window is significant for many optoelectronic devices. However, such versatility usually comes with additional unwanted power consumption. Here, we demonstrate transmittance-Tunable glass that operates without electrical power. The key element to the device is an axis-varying polarizer, which combines a photoalignment technique with dichroic dye self-Assembly mechanism. By linear translation of one patterned polarizer with respect to the other, different transmittance states can be achieved. Large-scale uniformity and relatively wide viewing angles (±60°) are also demonstrated. Furthermore, low-Temperature treatment (i.e., T < 80 °C) during fabrication demonstrates the device's potential to be made on the plastic substrate. The polarizer with patterned absorption axis can also be used as other optical components such as light amplitude shaping device. © 1989-2012 IEEE.

In this article, two different azo dye stabilization methods were demonstrated. One is realized by two-step exposure while the other is simplified one-shot irradiation on a thin film. Various stabilization methods provide more flexibility on alignment layer preparation. Both methods offer an alignment layer with highly acceptable thermal and photo-stability. © 2018 International Display Workshops. All rights reserved.

Broadband quarter wave plates are widely used in optical system, especially in display system. Above all, a broadband quarter wave plate can be treated as an isolator in display to provide “perfect” dark state so as to improve the contrast ratio. A kind of broadband quarter wave plate combined by two waveplates with angle deviated is proposed and manufactured in this paper using coating technique. Two methods of combination of the two waveplate are proposed and tried. The reflection spectrum shows that this kind of structure can provide good dark state in display system.