The design of volume holographic gratings (VHGs) is traditionally based on monochromatic plane waves. However, practical applications often involve light sources with broad wavelength bandwidths and certain emission areas, such as LEDs and MiniLEDs, which cause significant Bragg mismatch and degrade diffraction efficiency. To address this fundamental challenge, this paper proposes a novel, to the best of our knowledge, genetic algorithm (GA)-based optimization method for VHG design. A ray-tracing analysis model that fully incorporates the spectral and spatial characteristics of extended broadband sources is established. The GA optimizes the grating fabrication angles by minimizing a fitness function defined as the residual energy after diffraction, thereby achieving optimal performance under non-ideal illumination conditions. The effectiveness of the proposed method is demonstrated through a case study: suppressing the high-intensity central beam in an ultra-thin MiniLED backlight module (BLM). Simulation and experimental results show that the GA-optimized VHG significantly reduces the peak irradiance from 5.01 W/cm2 to 4.14 W/cm2 at an optical distance (OD) of 0.5 mm. This work provides a robust and source-adaptive design methodology for VHGs, with potential applications extending beyond backlighting to areas such as augmented reality, holographic displays, and optical communications.
Backlight units (BLUs) with miniLEDs as light sources can help improve display contrast and decrease the thickness of a liquid crystal display. Different from the current solutions of a diffuser film and secondary lens, the paper proposes a total-inner-reflection-based design method. The profile of a microstructure is decided when the powers of the rays reflected by the microstructure reach the maximum. Both simulated and experimental results show that uniformity can satisfy the requirement when the source-screen gap is 1 mm. With ultrathin thickness and no requirement for precise positioning, the designed miniLED BLU presents strong practicability.
In this work, we have made ultraviolet (UV) light visible by proposing and fabricating an integrated optoelectronic device. The demonstrated device consists of a GaN-based blue mini-light-emitting diode (mini-LED) and a phototransistor. The phototransistor is specially designed with an Al0.20Ga0.80N polarization gate. The background electrons can be depleted by the polarization gate to enable the normally-off state for the integrated optoelectronic device when there is no UV illumination. Our measured results show that when the polarization-gated phototransistor is switched off, the current for the integrated optoelectronic device is as low as 1.4 × 10-4 mA even when the device is biased to 10 V. Upon the 12.7 mW UV excitation, the current for the integrated device can be increased to 44.4 mA at the bias of 10.0 V. This enables the GaN-based visible mini-LED to generate the optical power of 81.1 mW. The largest power ratio between the UV excitation light and the mini-LED light of 49.8 times can be achieved, indicating the advantage of monitoring weak UV light by using the proposed design.
This study investigated observer metamerism and the predictive performance of CIE color matching functions (CMFs) in white-point matching tasks on wide-gamut displays with different technologies (LCD, Mini-LED, laser projector) but similar gamut sizes. Using a cross-display matching paradigm, 30 observers completed 9,300 matches to 56 reference stimuli sampled along the Planckian locus, spanning correlated color temperatures from 4000 K to 10000 K with varying Duv offsets. Experiments were conducted at 4° and 10° fields of view stimuli. The color difference between the visual matches was evaluated using the CIE 1931, CIE 1964, and the CIE 2006 CMFs with computational fields of view from 1° to 10°. The results reveal markedly larger inter-observer variability for narrowband laser projection, followed by Mini-LED displays, compared with conventional LCDs. The results indicate that variations in gamut area exhibit a limited effect on white-point matching performance, whereas the spectral characteristics of primaries highly influence the degree of cross-display color mismatches. Stimulus field of view critically determines optimal CIE 2006 CMFs parameters through "half-field effect": computational FOVs of 2°-3° minimize mismatch for 4° stimuli, while 4°-5° CMFs prove optimal for 10° stimuli. Such parameter misalignments, particularly when age deviations beyond 30 years for our 24-year-old cohort, substantially degrade predictive accuracy, with laser projectors exhibiting the severest sensitivity.
The GaN-based green miniaturized light-emitting diode (mini-LED) is a key component for the realization of full-color display. Optimized passivation layers can alleviate the trapping of carriers by sidewall defects and are regarded as an effective way to improve the external quantum efficiency (EQE) efficiency of mini-LEDs. Since AlN has a closer lattice match to GaN compared to other heterogeneous passivation materials, we boosted the EQE of GaN-based green flip-chip mini-LEDs through the deposition of a lattice-compatible AlN passivation layer through atomic layer deposition (ALD) and a SiO2 passivation layer through plasma-enhanced chemical vapor deposition (PECVD). Benefiting from reduced sidewall nonradiative recombination, the EQE of the green flip-chip mini-LED with a composite ALD-AlN/PECVD-SiO2 passivation layer reached 34.14% at 5 mA, which is 34.6% higher than that of the green flip-chip mini-LED with a single PECVD-SiO2 passivation layer. The results provide guidance for the realization of high-performance mini-LEDs by selecting lattice-compatible passivation layers.
Transparent meltable glasses are keenly desired for making color-conversion layer of Mini-LEDs. In this work, transparent luminescent organic glasses were prepared using a new matrix of heptyltriphenylphosphonium bromide (C25H30BrP, HTPBr). Through doping of a blue dye (9,10-diphenylanthracene, DPA), the resulting glass exhibited a high transparency (92%) and a blue emission at 436 nm. Importantly, the PL QY of glass reached up to nearly unity under 398-nm excitation. X-ray diffraction (XRD) measurement confirmed the amorphous nature of the glass. Thermal characterization revealed a glass transition temperature (Tg) of 28 °C, a melting temperature (Tm) of 178 °C, and a thermal decomposition temperature of 270 °C. Apart from the blue-emitting glass, green- and red-emitting glasses of high transparency were synthesized varied chromophores, including 9,10-bis(phenylethynyl)anthracene (BPEA) and rhodamine B. In a proof-of-concept experiment, these glasses were used to encapsulate UV LEDs via a simple dipping process, which showed a satisfactory color rendering ability. This work brought a new member into the family of transparent luminescent glasses, promising many applications in areas including full-color displays and large-area mini-LED panels.
Visible light communication (VLC) is promising for next-generation communication, often integrated into lighting or a display to constitute a multifunctional system. Such a system usually has a large-scale LED matrix as input and plural functions to be optimized. In contrast, current design methods for VLC are limited to very few inputs and two objectives with a clear trade-off relationship. Regarding the limitation, this study proposes a new design optimization method for an integrated display and communication (IDAC) system. The IDAC system integrates VLC into a mini-LED LCD, whose hundreds of backlight segments act as independent transmitters to form a multi-input, multi-output (MIMO) VLC system. The mini-LED backlight also enables fine local dimming for higher display contrast and lower power consumption. Thus, modulation of the LEDs simultaneously affects VLC capacity, power consumption, and image distortion. To address this multi-input and three-objective problem, we adopt the MOEA/D (multi-objective evolutionary algorithm based on decomposition) framework. Considering the large input number, we propose a uniform sampling strategy in the three-dimensional solution space for evenly distributed solutions on the Pareto front. As a result, by comparing with conventional local dimming algorithms (Max, Average, and Square Root algorithms), the proposed method exhibits the most comprehensive performance: balanced image distortion and power consumption, as well as the highest spectral efficiency for VLC. The display and VLC performances are verified on an IDAC prototype by taking photographs with a CMOS camera to observe the stripes produced by the rolling shutter effect.
In the production of mini-light-emitting diodes (LEDs), chromatic discrepancies among chips have become a significant factor affecting display quality. The hybrid chip sorting method is commonly employed in mini-LED production to achieve efficient demura, but a comprehensive evaluation system is lacking. This study evaluates the chromatic uniformity of mini-LED arrays using a gray-level co-occurrence matrix (GLCM) and the discrete Fourier transform (DFT). A scientific evaluation system was established to assess the chromatic uniformity of displays. Data from 270 wafers were collected to construct a comprehensive mini-LED arrays database. Experimental results demonstrate that this evaluation system accurately assesses texture information within images, revealing chromatic differences in local details as well as overall uniformity and periodic variations. These analytical methods are expected to effectively support the optimization of binning processes, enhance demura efficiency, and provide a scientific basis for process improvement and quality control.
Visual behaviour in zebrafish, often measured by the optokinetic reflex (OKR), serves as a valuable model for studying aspects of human neurological and ocular diseases and for conducting therapeutic or toxicology assays. Traditional methods for OKR analysis often rely on binarization techniques (threshold-based conversion of images to black and white) or costly software, which limits their utility in low-contrast settings or hypopigmented disease models. Here, we present a novel deep learning pipeline for OKR analysis, using ResNet-50 within the DeepLabCut framework in a Python Version 3.10 environment. Our approach employs object tracking to enable robust eye movement quantification, regardless of variations in contrast or pigmentation. OKR responses were elicited in both wild-type and slc45a2 (albino) mutant zebrafish larvae at 5 days post-fertilisation, using a mini-LED arena with a rotating visual stimulus. Eye movements were recorded and analysed using both conventional software and our deep learning approach. We demonstrate that the deep learning model achieves comparable accuracy to traditional methods, with the added benefits of applicability in diverse lighting conditions and in hypopigmented larvae. Statistical analyses, including Bland-Altman tests, confirmed the reliability of the deep learning model. While this study focuses on 5-day-old zebrafish larvae under controlled conditions, the pipeline is adaptable across developmental stages, pigmentation types, and behavioural assays. With appropriate adjustments to experimental parameters, it could be applied to broader behavioural studies, including social interactions and predator-prey dynamics in ocular and neurological disease models.
This paper demonstrates the use of organic thin-film transistors (OTFTs) to drive active digital mini light-emitting diode (mini-LED) backlights, aiming to achieve exceptional display performance. Our findings reveal that OTFTs can effectively power mini-LED backlights, reaching brightness levels exceeding 100,000 nits. This approach not only enhances image quality but also improves energy efficiency. OTFTs offer a flexible and lightweight alternative to conventional silicon-based transistors, enabling innovative and versatile display designs. The integration of mini-LED technology with OTFTs produces displays with superior contrast ratios, enhanced color brightness, and lower power consumption. This technological advancement is poised to revolutionize high-dynamic-range (HDR) displays, including those in televisions, smartphones, and wearable devices, where the demand for high brightness and energy efficiency is paramount.
Femtosecond laser has greatly enabled the development of high-resolution, high-aspect-ratio and damage-free nano-processing. In this study, we adopted single- and multifocal femtosecond laser stealth dicing to fabricate the on-wafer GaN-based mini-LEDs grown on sapphire. Due to the difference in energy distribution between single-focal and multifocal lasers, there would be no oblique cracks of crystal and edge-breakage of mini-LEDs in the unsyncrystalline orientations of sapphire by using multifocal femtosecond lasers. Due to the higher aspect-ratio of a multifocal femtosecond laser, the narrower slicing-width means the production yield of 80 × 120 µm2 mini-LED on a 4-inch wafer could increase by 14.6%. In addition, for the morphology of the sidewall of sapphire, there would be higher symmetry light-patterns and brighter luminance in the mini-LEDs sliced by using multifocal-lasers. Moreover, the dispersed focal result in the relatively low energy density between the sapphire substrate and the epitaxial layer, thus the ablative perforation-induced current leakage in several mini-LEDs could be greatly reduced, and the yield of devices could be improved. These results may give a reference for the field of semiconductor manufacturing and displays.
A novel four-in-one (4-in-series) MicroLED-in-Package (MiP4) architecture is demonstrated for the first time, integrating four sub-85 µm blue micro-LED (µ-LED) dies on a transparent glass substrate through a redistribution-layer (RDL) interconnection process. The MiP4 device operates natively at 16 V, eliminating the need for step-down converters and simplifying high-voltage backlight driving circuits. The transparent glass carrier enables efficient light extraction, excellent thermal dissipation, and uniform emission. Electrical and optical characterization of dual- (B2), triple- (B3), and quad-chip (B4) devices shows ideal voltage scalability (8 V, 12 V, 16 V) and stable emission at 450 ± 2 nm with minimal FWHM broadening (22-29 nm). Compared with a commercial LED, the MiP4 delivers 1.8× higher optical power (~41.8 mW) despite its active area being only ~1/70 that of the reference device (20,000 µm2 vs. 1,350,000 µm2), yielding a dramatically enhanced luminous flux density of 64 lm/mm2 at 50 mA. Furthermore, pulse-driven measurements under 2%, 5%, and 10% duty cycles verify excellent thermal stability and minimal spectral shift (<1 nm), confirming the device's robustness and energy efficiency. This first-of-its-kind 4-in-1 high-voltage glass-based µ-LED package provides a scalable and manufacturable route toward next-generation ultra-thin, high-brightness Mini-LED backlight and optical communication systems.
Iodide-bromide mixed perovskites have attracted significant attention for achieving pure-red emission. However, halide migration hinders the development of efficient and stable devices. We introduce an in situ crystallization regulation strategy using post-annealing to optimize pure-red CsPb(Br/I)3/PVDF composite films. This process controls thermally induced halide migration, promotes regrowth, enhances crystal quality, and optimizes halide distribution. Consequently, the photoluminescence quantum yield increases from 9.3 % to 33.2 %, one of the highest reported values for pure-red mixed halide perovskite quantum dot films. When integrated with blue Mini-LEDs, the optimized film produces a backlight device exceeding 129 % of the NTSC color gamut standard. These findings advance the practical application of perovskite quantum dots in next-generation displays and pave the way for stable pure-red emitters, crucial for enhancing color gamut coverage and achieving high-resolution displays.
The continuous upgrading of partition backlight technology has brought new competitive advantages to LCD, making it comparable to OLED in display performance, such as high contrast. Because the LCD does not have an ideal turn-off characteristic, there will be a halo phenomenon when local dimming is turned on. Due to the low luminance value of the halo and glare interference of the luminance meter, the actual light distribution is difficult to measure, so previous studies on halo effect characterization were mostly based on simulation or qualitative analysis. This paper first gives a method to accurately measure the halo distribution by using a mask to cover the center luminous region to avoid glare interference generated by the normal luminance meter. Based on the measured halo distribution and its correlation with the subjective assessment on halo visibility, a halo visibility estimation model was established, which quantifies the impact of display luminance, panel transmittance, and backlight unit (BLU) size. The predicted value of this model was highly correlated with the subjective experiment data, with a good fit of R2=0.92. With this model, the halo visibility with any combination of panel sizes, initial contrast ratios, and BLU numbers can be easily calculated.
High-efficiency GaN-based green miniaturized light-emitting diodes (mini-LEDs) are of great significance to the development of full-color high-resolution displays. Here, a double-sided hemisphere-shaped patterned sapphire substrate (PSS) was fabricated for improving the external quantum efficiency (EQE) of green flip-chip mini-LEDs using nanoimprint lithography (NIL). We find that the hemisphere-shaped microstructures are more effective at extracting light into the air compared to the frustum-shaped and cone-shaped microstructures. Furthermore, the green flip-chip mini-LED with double-sided hemisphere-shaped PSS has a more uniform distribution of light-emitting intensity than that with single-sided hemisphere-shaped PSS. The EQEs of the green flip-chip mini-LEDs with single-sided hemisphere-shaped PSS and double-sided hemisphere-shaped PSS were 27.02% and 33.09% at 5 mA, respectively. Finite-difference time-domain simulations show that the double-sided hemisphere-shaped microstructures can increase the total light extraction efficiency (LEE) of green flip-chip mini-LED by 17.39% compared to the single-sided hemisphere-shaped microstructures.
Water-soluble quantum dots (QDs) are necessary to prepare patterned pixels or films for high-resolution displays with less environmental burden but are very limited by the trade-off between photoluminescence and stability of QDs. In this work, we proposed synthesizing water-soluble QDs with simultaneous excellent luminescence properties and high stability by coating the amphiphilic poly(maleic anhydride-alt-1-octadecene)-ethanol amine (PMAO-EA) polymer on the surface of silane-treated QDs. These coated QDs show a photoluminescence quantum yield (PLQY) as high as 94%, and they have good photoluminescence stability against light irradiation and thermal attacks, owing to the suppression of the nonradiative recombination by the polymer layer and the isolation of oxygen and water by the silica layer. The water-soluble QDs, mixed with ethylene glycol, enable inkjet printing of QD color conversion films (QD-CCFs) with an average diameter of 68 μm for each pixel and a high PLQY of 91%. The QD-CCFs are demonstrated to fabricate red-emitting mini-LEDs by combining with blue mini-LED chips, which have an external quantum efficiency as high as 25.86% and a luminance of 2.44 × 107 cd/m2. We believe that the proposed strategy is applicable to other water-soluble QDs and paves an avenue for inkjet printing environmentally friendly QD-CCFs for mini/micro-LED displays.
Urinary tract infection (UTI) is a common and prevalent disease caused by a spectrum of pathogens. Lack of access to rapid, portable, and high-quality diagnostics in resource-limited settings aggravates the improper treatment of UTIs, which is also a major driver of antibiotic misuse worldwide. Here, we describe a custom-made portable colorimetric array (PoCA) for reading out polymerase chain reaction (PCR) amplicons, the rationale of which is to transfer the previously developed dsDNA-based photosensitization colorimetric assay (solution) onto paper discs for detection. By integrating mini-LED irradiation and paper discs, the PoCA can read out 96 PCR tests in one pot, thus allowing diagnosis and identification of 12 prevailing UTI pathogens in less than 2 h, coupled with a portable thermal cycler for PCR. After analyzing 200 clinical urine samples, the pathogen profiling accuracy of the PoCA was demonstrated to be higher than the standard urine culture (confirmed with metagenomic next-generation sequencing). The PoCA platform could be used in primary care for rapid UTI diagnosis and pathogen identification.
AlGaInP-based red light emitting diodes (LEDs) are considered as promising light sources in future full-color displays. At present, vertical chip configuration is still the mainstream device structure of AlGaInP-based red LEDs. However, current crowding around p-electrode severely hinders an efficient improvement. Here, we propose a Schottky-contact current blocking layer (SCBL) to enhance current spreading and to improve light extraction efficiency of AlGaInP-based red vertical miniaturized LEDs (mini-LEDs). By utilizing the Schottky contact between ITO and p-GaP, the SCBL can hinder current crowding around the p-electrode. The current is forced to inject into an active region through a p-GaP+ ohmic contact layer, avoiding light absorption by p-electrode. Through the transfer length method, the Schottky contact characteristics between the ITO and p-GaP as well as the ohmic contact characteristics between ITO and p-GaP+ are demonstrated. Benefiting from superior current spreading and improved light extraction, a mini-LED with SCBL realizes an enhancement of 31.8% in external quantum efficiency (EQE) at 20 mA in comparison with a mini-LED without SCBL.
Mini-LED backlight has emerged as a promising technology for high performance LCDs, yet the massive detection of dead pixels and precise LEDs placement are constrained by the miniature scale of the Mini-LEDs. The high-resolution network (Hrnet) with mixed dilated convolution and dense upsampling convolution (MDC-DUC) module and a residual global context attention (RGCA) module has been proposed to detect the quality of vehicular Mini-LED backlights. The proposed model outperforms the baseline networks of Unet, Pspnet, Deeplabv3+, and Hrnet, with a mean intersection over union (Miou) of 86.91%. Furthermore, compared to the four baseline detection networks, our proposed model has a lower root-mean-square error (RMSE) when analyzing the position and defective count of Mini-LEDs in the prediction map by canny algorithm. This work incorporates deep learning to support production lines improve quality of Mini-LED backlights.
Visible light communication (VLC) can be integrated into a liquid crystal display (LCD) by modulating its backlight while normally showing pictures. Received by ordinary cameras, such integrated display and communication (IDAC) systems are promising for the Internet of Things and Metaverse. However, in the premise of unaffected display function, the capacity of current IDAC systems is limited, with data rates of very few kbps. This work proposes a new architecture: multiple-input, multiple-output (MIMO) VLC integrated into a mini-LED LCD, whose many backlight segments act as multiple transmitters. A camera utilizes the rolling shutter effect with independent pixel columns to form multiple outputs. The communication capacity is thus significantly multiplied by the backlight column number. In addition, local dimming, which is favorable for an LCD's contrast and power consumption, is exploited to achieve efficient signal modulation. We built a mini-LED LCD prototype with 8-by-20 backlight segments for experimental verification. The backlight segments multiplex a video-rate signal for local dimming and a high-frequency (∼34 kHz) signal modulated through multi-pulse position modulation (MPPM) for VLC. By taking photographs with a camera 1.1 m away from the screen, a record-high rate of 201.6 kbps (approximately ten times faster than current IDAC systems) was experimentally achieved with a bit error rate satisfying the forward error correction. Improved image contrast due to local dimming was also observed.