Journal of the Society for Information Display最新文献

This study investigates the angular dependence of far-field electroluminescence (EL) emission in InGaN/GaN LEDs and micro-LEDs to enhance their performance for micro-display and visible optical communication applications. We developed a measurement setup to analyze far-field EL emission across various wavelengths and compared the results with 1D optical simulations. This approach allowed us to observe the well-known dependence of emission directivity and light extraction efficiency (LEE) on the structural parameters of flip-chip LEDs, particularly the thicknesses of p-GaN and n-GaN layers, and to quantify the impact of total thickness variation resulting from wafer thinning processes. Using larger LEDs, the test vehicle offers a valuable tool for designing micro-LEDs with the desired directivity and for process monitoring. We also observed that the angular dependence of far-field emission varies with the applied bias and demonstrated how this could affect wafer-level micro-LED characterizations. Finally, we showed that the far-field EL emission of micro-LEDs progressively deviates from the description by a 1D optical cavity alone, suggesting an increasing influence of the limited size and necessitating 3D-FDTD simulations to accurately model both vertical cavity and sidewall effects. However, for sizes down to 5 μm, the directivity predicted by a 1D model seems roughly preserved.

In this work, a system for the real-time spatially resolved detection of visible light on a large area is realized on glass. Schottky photodiodes, consisting of hydrogenated amorphous silicon (a-Si:H) and molybdenum–tantalum (MoTa), are employed as detectors. The detectors exhibit an internal quantum efficiency of up to 70.96% and a response time smaller than 20 μs. The noise equivalent power was measured at 2.424e-10 W/√Hz. Process compatibility with commonly employed amorphous indium gallium zinc oxide (a-IGZO) and a-Si:H thin-film transistors (TFT) is shown. The driving and real-time readout of a photosensor array is demonstrated using a microcontroller and a current-input ADC.

High-resolution printing technology is crucial for electroluminescent (EL) quantum dot light-emitting diodes (QD-LEDs) to be used in high-end display applications such as AR/VR displays. This study successfully demonstrates the patterning of PEDOT:PSS, ZnO nanoparticles (NPs), and InP-based QD/organic nanohybrids using electrohydrodynamic (EHD)-jet printing, fabricating top-emitting green conventional or inverted QD-LEDs on a PEN flexible substrate. The integration of a hydrophobic pixel defining layer and continuous-jet modes in the EHD-jet printing system enhances the patterning processability, showcasing the EL of patterned conventional and inverted QD-LEDs. Especially, the EL spectrum of an inverted QD-LED exhibits a sharp green emission at a peak wavelength of 542 nm, with a full width at half maximum (FWHM) of 46 nm. This indicates that the uniform layers were achieved through EHD-jet printing and balanced charge carriers in the device, despite the active layer consisting of not only InP-based QDs but also n-type and/or p-type organic transport materials. This research opens up new possibilities for the utilization of EHD-jet printing in various QD-LED structures for commercially viable printed display applications.

State-of-the-art displays are emerging with a technology called variable refresh rate (VRR) that supports a wider range of refresh rates, both above and below 60 Hz. While VRR can reduce power consumption, it can cause flicker issues for users when the refresh rate is lowered below 60 Hz or when the refresh rate is changed even above 60 Hz. Since users can perceive both types of flicker as similar image artifacts, we developed the integrated flicker index to predict them. We introduced time-domain analysis using impulse response functions (IRFs) to capture the onset of aperiodic luminance fluctuations in the VRR waveform and interpret human response to these fluctuations. In addition, based on the previous studies that display characteristics (e.g., luminance and size) affect flicker experience, we need to incorporate both effects of brightness and size into IRF. For this purpose, we utilized the converted IRFs from the TCSF model, which can explain these two effects. To validate the integrated flicker index, we conducted three experiments: flicker when the refresh rate is reduced below 60 Hz flicker (Exp1 and 2) and VRR flicker when the refresh rate is changed (Exp3). The results demonstrate that IRF converted from the appropriate TCSF could offer a more accurate prediction of flicker experience of VRR displays.

This paper presents a newly developed process for interconnecting microICs with microLEDs through ultra-precise dispensing of conductive silver-based paste. Special cleaning and surface energy modification processes have been introduced to achieve interconnects with a width of 5 μm and a minimum pitch of 20 μm. The developed technology is part of the EU funded project “Building Active matrix MicroLED displays By Additive Manufacturing” (BAMBAM), which develops unique manufacturing technologies for realizing microLED displays without TFT backplanes.

With the rapid expansion of data centers, there is a growing demand for high data-rate, energy-efficient optical links over short distances. One potential technology for this application is Gallium-Nitride (GaN) based microlight emitting diodes (μLEDs), thanks to their compact size, high-speed operation, and ease of manufacturability. During the development of these μLEDs, modeling plays an essential role in optimizing their performance. In this paper, we present various models to estimate both the static and dynamic performance of GaN μLEDs of various sizes. We then propose a methodology to integrate these models into a unified equivalent circuit model, enabling the simulation of the full response of the μLED. Finally, we implement this unified model in a circuit-simulation-compatible module and replicate the experimental setups within a simulation software to evaluate the module's ability to accurately simulate the μLED's response.