Technical / research

MicroLED-Connect is an upcoming hybrid event series, a year-long program of virtual and onsite events, all focused on the microLED industry. The first MicroLED Connect virtual event is coming up later this month, a 2-day virtual event that will be focused on microLED (and also miniLED) technologies. The event will include over 25 lectures from leading companies, researchers and market analysts. The series is organized by the MicroLED Industry Association together with TechBlick.

In this post we share three online presentations, taken from last year's online microLED event (November 2022). The first video, above, is from the SSLEEC group (led by Prof. Denbaars and Prof. Nakamura) at the University of California, Santa Barbara, that discusses the latest microLED research performed at this world-renowned group. 

Researchers from Shanghai Jiao Tong University together with UK-based OTFT developer SmartKem published a new paper describing the use of via interconnections in an organic-last integrated microLED display. The researchers report that the low-defect organic semiconductor backplane enables excellent performance.

As part of the project, the researchers demonstrated a 254 PPI active-matrix microLED display that achieves a brightness of 150,000 nits. The transistors exhibit superior performance in terms of milliampere driving current, and large ON/OFF current ratio approaching 10¹⁰ with excellent uniformity and reliability

Researchers from the Korea Photonics Technology Institute (KOPTI) have developed highly efficient microLED devices. the researchers say that these new LEDs maintain an IQE of over 90% and are not effected by small chip site and increased current density.

The new microLEDs, branded as ZOGAN LEDs, are made from p-ZnO and p-GaN. The researchers say that the non-radiative leakage current is almost negligible and not increased as the chip size decreases even below 10 um. The researchers created blue ZOGAN LEDs in sizes 5, 10 and 20 um and confirmed the high performance in all these devices.

Researchers from the  Universidad Politécnica de Madrid and MIT, published a review article on Micro-Scale Concentrating Photovoltaics, or micro-CPV, a new technology that uses miniaturized solar panels and optics that concentrate the sun's energy into these micro panels. The benefits of micro-CPV compared to normal solar panels include potentially lower cost (much less solar absorption area), better thermal management, shorter optical path and lower resistive losses.

There are many challenges yet before micro-CPVs can be produced in large volume and at competitive prices. Interestingly, microLED production processes can be applied to the production of micro-CPVs, as these solutions can be seen like inverted technologies - tiny devices that either absorb or emit light.

Researchers from Korea's ETRI institute developed a new chip packaging material, that is said to reduce the power consumption of the process by 95%, and reduce the number of required stages from 8 to 3. This could make semiconductors production much more efficient and lower in cost. 

The technology is applicable to all high-end semiconductor production - including microLED production. Indeed the team reports that they have reached out to several microLED developers to evaluate the technology, and the initial testing has been very positive. The material could be commercialized in three years.

Researchers from Seoul National University, in collaboration with LG Electronics, developed a new transfer process for microLED displays, based on a fluidic process.

The new process, called Fluidic Self‑Assembly (FSA), starts with a collection of microLEDs (chiplets) dispersed in an assembly solution, and a display substrate in which the binding targets are coated with molten solder. The substrate is immersed in the fluid, and then the fluid is set in motion (is shaken), which causes the microLED chiplets to make repeated contact with a binding targets. When a microLED chiplet meets the binding target, surface tension induces an irreversible bond between the solder and a metal electrode on the chiplet.

Toray Industries announced that it has developed a new conductive bonding material that works at lower temperatures (110 degrees Celsius) and pressures (5 megapascals) compared to existing materials, and is suitable for microLED processes. 

Toray's new material is based on the company's RAYBRID photodefinable conductive material (produced from metals, glass, ceramics and other materials), combined with nanocarbon and adhesives. The company plans to start producing the new material by early 2025.

Researchers from the UK-based University of Strathclyde, led by Dr. Eleni Margariti, developed a new microLED transfer process, based on a continuous, single shot roller transfer printing process.

The researchers say that this process can enable large-scale integration of microLEDs. The system they developed can transfer an array of 320x240 pixels (over 75,000 microLEDs) in a single shot, with sub-micron relative position accuracy. The transfer printing process preserves the array geometry with pixel spatial location error less than 1 µm deviation from the as-designed layout. 

The researchers also employed an automated sub-micron precision metrology system based on simple optical microscopy, to asses such large device populations and allow the assessment of yield.

Researchers at MIT have developed a bottom-up approach for precise and scalable formation of perovskite nanocrystal arrays with deterministic control over size, number, and position. This new technology enables the deposition of halide perovskite nanocrystals with precise control over the location and size of each individual crystal, integrating them into nanoscale light-emitting diodes.

The researchers demonstrated deterministic arrays of CsPbBr3 nanocrystals with tunable dimensions down to <50 nm and positional accuracy <50 nm.