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The continuous miniaturization of micro-LEDs poses challenges for yield testing using electrical contact probes. Single-ended electrical contact micro-LEDs (SEC-LEDs), as a special noncontact alternating current (ac) device, have advantages, such as not relying on probes and simple electrode design. It also solves the carrier injection problem in traditional ac drive LEDs, making it have great potential in the field of nondestructive testing of chips. However, the low luminous intensity of SEC-LED is still the bottleneck problem restricting the application of SEC-LED in the field of detection. In this study, an optimized driving waveform strategy is proposed to enhance the electroluminescent intensity of SEC-LED from a driving technology perspective. By establishing an equivalent circuit model and combining simulation analysis of its working mechanism, the impact of circuit parameters on current is further analyzed, leading to the derivation of corresponding current-domain equations. The simulation and experimental results illustrate that a higher rate of voltage change and a larger circuit capacitance are advantageous for increasing the forward peak current of SEC-LED. Square waves, with their highest rate of voltage change over time, have been identified as the optimal driving waveform for achieving high luminous intensity in SEC-LED. When driven by square waves at the optimal frequency point, the peak luminous intensity is increased by up to 266% compared to traditional sine wave driving. Therefore, this proposed optimization strategy effectively enhances its luminous performance and holds broad application prospects in micro-LEDs high-precision detection fields.

Light-emitting diode (LED) display devices that combine high light extraction efficiency (LEE) and high ambient contrast ratio (ACR) are the key to achieve high-performance displays. At present, the industry usually can only meet one performance at the expense of the other. In this article, a simple optical performance regulation method that does not require additional energy drive was implemented, by integrating photothermal actuation structure (PAS) into LED display devices to improve their LEE and ACR. Specifically, a PAS based on graphene oxide (GO) and polydimethylsiloxane (PDMS) (GO-PDMS PAS) was designed. The GO layer plays a role in extinction, which can reduce the reflectivity of LED display devices, thereby improving ACR. The PDMS layer and the GO layer jointly play a role in photothermal deformation; by absorbing the optical energy of LED display devices, the GO-PDMS PAS gradually opens, improving the LEE. Compared with the commercial LED display device using the graphite as extinction layer (GPH-LED), the ACR and LEE of the LED display device using the GO-PDMS PAS as extinction layer (PAS-LED) were improved by 437% and 150%, respectively. In the future, scholars can further study and optimize the structure of the PAS and design it in combination with other functional materials, thereby further improving the LEE and ACR of LED display devices.

The voids distribution uniformity within the bonding layer has emerged as a critical factor affecting thermal reliability of light-emitting diodes (LEDs), while the absence of quantitative characterization poses challenges in accurately assessing its impact and optimized design. In this study, a calculation method for the uniformity coefficient of the bonding layer voids distribution is proposed, revealing the impact of voids uniformity on the thermal performance of the device. We have investigated the influence of the number of voids and divided grids on the uniformity coefficient, establishing the criterion of saturated grid number. Results show that the decrease of the voids distribution uniformity coefficient leads to a lower thermal resistance and junction temperature, demonstrating that more uniformly distributed voids in the bonding layer are beneficial to improve the heat conduction path. This work reveals a significant correlation between the thermal performance of LED devices and the voids distribution uniformity coefficient, providing valuable insights for understanding and controlling the voids distribution to achieve effective heat dissipation of such devices.

High-efficiency mini-LED with a large light-emitting angle is the key to achieving high-quality high dynamic range (HDR) in liquid crystal display (LCD) displays. In this study, we adopted photolithography and ion beam-assisted electron beam evaporation to prepare a dome-shaped SiO2/Al2O3 composite-patterned sapphire substrate (CPSS). Simultaneously, inductively coupled plasma (ICP) dry etching was used to form a patterned sapphire substrate (PSS) as the contrast group. Combined with epitaxial growth and chip manufacturing processes, mini-LED flip chips prepared using CPSS and PSS were obtained, and mini-LED backlight modules were prepared. By comparison, we found that the CPSS-LED chip has higher external quantum efficiency (EQE), and higher EQE brings higher peak brightness, which improves the HDR performance. Simultaneously, we also found that the CPSS-LED chip has a larger light-emitting angle, and the mini-LED backlight module made of it shows a more uniform irradiance distribution and better light mixing effect. In short, we prepared a high-performance mini-LED backlight module using the CPSS-LED chip with both a large light-emitting angle and high EQE, which is expected to be used in future LCD displays.

A high ambient contrast ratio (ACR) is essential for achieving a high dynamic range in advanced display applications, but reported ACR enhancement strategies always result in reduced optical efficiency of light-emitting diode (LED) display devices. In this study, an Fe3O4-magnetic particle-chained pillar array (Fe3O4-MPCP) structure was introduced to improve the ACR of LED display devices with low optical loss. The results indicated that the MPCP structure achieved high ACR at an oblique angle using surface pillar array to suppress ambient light reflections, and its internal magnetic particle chain improved the transmissivity to maintain high device efficiency. Compared with the commercial graphite-coated device at typical viewing angles (i.e., 0 deg and 60 deg), the ACR of the optimal MPCP device increased by 217 and 140%, while the device efficiency increased by 25 and 12%, respectively. Therefore, the proposed method provides a novel approach for significantly improving ACR at all oblique angles while maintaining high device efficiency, which can be easily integrated into various LED display devices and has significant potential in advanced display applications.

In this study, we analyze the influence of the pore structure of an SBA-15 particle on the light emission from its inner adsorbed quantum dots (QDs) and outer light-emitting diode (LED) chips. It is found that the particle features of a high refractive index, comparable feature size of pore structure, and lower amount of QD adsorption help with QD light extraction, demonstrating a mechanism to suppress QD light propagating through pores and thus reducing the reabsorption loss. We consequently developed highly efficient QD white LEDs with wet-mixing QD/SBA-15 nanocomposite particles (NPs) by further optimizing the packaging methods and the introduced NP mass ratio. The LEDs demonstrated a record luminous efficacy (the ratio of luminous flux to electrical power) of 206.8 (entrusted test efficiency of 205.8 lm W–1certificated by China National Accreditation Service) and 137.6 lm W–1at 20 mA for white LEDs integrating only green QDs and green–red QD color convertors, respectively, with improved operating stability. These results are comparable to conventional phosphor-based white LEDs, which can be a starting point for white LEDs only using QDs as convertors toward commercialization in the near future.

LED has been regarded as the next generation lighting source. As for high power LED lamps, heat accumulation will cause a series of problems. Therefore, thermal management is very important for designing a high power LED lamp. Three types of heat sinks are designed by using the finite element analysis (FEA) method for an 180W high power LED lamp. Then the optimized heat sinks are developed and experiments are performed to demonstrate the simulated results. At the same time, the thermal performances with different working angles are investigated experimentally. The heat sink with heat pipe has a better heat dissipation performance than the conventional heat sink under the same input power. The working angles of the lamps greatly influence the thermal performance of each heat sink. For the same heat sink, the temperature varies with different install directions and working angles. Finally, the heat sink with the best thermal performance is recommended. The results have practical significance in designing high power LED lamps.

The cepstrum edit scheme for the vibration feature extraction of the faulty rolling element bearing (REB) is studied in this paper. By combined the time synchronous average (TSA) and the real cepstrum to localize and edit the cepstral lines of the original vibration, the unwanted discrete frequency components can be removed. Then, a corresponding inverse procedure is designed, in which the edited cepstrum and the original phase spectrum are employed to reconstruct the edited vibration for the REB feature extraction. Simulation verified the scheme positively.

Mini full-color light-emitting diodes (mini-fc-LEDs) are a promising solution for display applications, including outdoor, cinema, and wearable devices, owing to their high resolution. However, it is difficult to simultaneously obtain high color uniformity and ambient contrast ratio (ACR). To solve this issue, we report a bilayered packaging structure with an SiO2 scattering layer on the bottom and a graphite extinction layer on the top. The bilayered packaging structure combines the scattering effect of SiO2 nanoparticles and the extinction effect of graphite nanoparticles, wherein the scattering effect improves the color uniformity, and the extinction effect improves the ACR. The color uniformity and ACR of the mini-fc-LEDs were selectively adjusted by changing the nanoparticle concentration and the thickness ratio of the bilayer. Compared to conventional devices, the inhomogeneity of the bilayered devices reduced by 65.9%, the ACR increased by 32.9%, and the figure of merit (FOM, representing the overall performance of the device) increased by 168.8%. We believe that the proposed packaging structure can also be applied to other LEDs such as OLEDs and micro-LEDs.

Results of autocorrelation analysis algorithm by the LabVIEW are different from the theoretical results. To address the problem, a modification of autocorrelation analysis is proposed in this paper. In the proposed approach, the circular correlation and linear compensation are employed to solve the distortion problem in the original algorithm. Simulation results show that the method can reduce errors of autocorrelation analysis effectively.

Inverted packaging structure is a promising alternative for thermal isolation between light-emitting diode (LED) chips and quantum dot (QD) converters with effective heat dissipation. However, serious reflection loss occurs at the lead frame owing to the inverted bonding of LED chips. In this study, the scattering nanoparticles-induced reflection effect has been developed to enhance the optical efficiency of inverted QD-LEDs combined with the centrifugation technique. The strong back-scattered effect of boron nitride (BN) nanoparticles with a thin columnar structure is chosen for reflection enhancement according to the ray-tracing and finite different time-domain simulations. Furthermore, a centrifugation technique is introduced to control the equilibrium geometry of the BN-incorporating reflector (BNR) by changing the centrifugal speed. Results indicate that the luminous flux of inverted QD/BNR-LEDs using the optimized concave BNR structure largely increases by 82.8% compared with reference inverted QD-LEDs. The great enhancement is attributed to the light concentrated effect of the concave geometry and the strong diffusion reflection ability of BN scattering nanoparticles. Consequently, the smart design on reflection properties of inverted QD-LEDs is critical for achieving high optical performances.

Quantum dot (QD) attracts great attention in light-emitting diode (LED) packaging for high-quality light sources, while it leads to low light efficiency due to the significantly high reabsorption loss between QDs. Accordingly, we experimentally study the reabsorption properties of QD color convertors (QCCs) for LED packaging considering various thicknesses and concentrations under different injection current. The results indicate the QCC configuration with a small thickness and large concentration can have the same absorption ability for chip light as that with the opposite configuration, resulting in the same QD light proportion. However, the QCC configuration having smaller thickness is more useful to decrease the reabsorption loss, leading to higher radiant power (an increase of larger than 37.2%). Moreover, it is essential to gain a high radiant power of QD light with small reabsorption loss, which can be realized by combining QCCs with a low QD content and a source with a large injection current. Based on this simple and effective approach, a conversion loss smaller than 20%, close to their quantum yield, can be achieved, which is approximately four times smaller than that gained by QCCs with a high QD content. However, it introduces additional radiant power of chip light, suppressing further improvement in the QD light proportion. Much work is still required to make full use of the redundant chip light. This study provides a better understanding of the reabsorption properties of QCCs and can significantly accelerate their applications in illumination and display applications.