stacked emitters

China-based microLED developer Westlake Smoky Mountains Technology has finalized its pre-A series funding round, raising almost 100 million Yuan (around $14 million USD). Several VCs participated in this round, including Shenzhen Capital Group (SCGC), Ivy Capital, Moganshan Fund, and Lenovo Capital & Incubator Group.

WSMT developed a vertically stacked microLED architecture, targeting both microdisplays and direct-view displays. The technology originates from Hangzhou's Westlake University. The company is building a small-scale epiwafer production line in Huzhou, Zhejiang Province, China, and aims to start production by the end of 2025.

China-based Innovision, developer of microLED microdisplays based on the company's vertically-stacked pixel (VSP) technology, announced that it has started to produce microdisplays in its production line. 

Innovision started building its production line in March 2024, and soon afterwards the company demonstrated an XGA vertically-stacked full color display, that offers a brightness of over 500,000 nits.

During Display Week 2023, Seoul Semiconductor demonstrated new prototype display modules that use its WICOP microPixel technology. WICOP Pixel is a full-color one-chip vertically-stacked microLED technology that does not require wire bonding, packaging, or lens, and enables easier microLED display production.

Seoul Semi updates that its latest WICOP Pixels reach a brightness of 10,000 nits (up from 4,000 in its previous generation technology).

Researchers from the US and Korea, led by MIT, developed full-color vertically-stacked microLEDs that achieve the highest array density (5100 PPI) and the smallest size (4 µm) reported to date.

To end up with such high resolution and small microLED chip size, the researchers used a 2D materials based layer transfer (2DLT) technique. The resulting microLEDs, that have near-submicron thickness, are grown on 2D material-coated substrates, removed, and then stacked.

Specialized Korea-based LED developer Lumens announced that it has developed a Monolithic RGB epitaxial wafers for micro-LED display production. The new technology stacks the three color LEDs on on top of the other on the wafer.

A comparison between Lumen's stacked RGB transfer process (bottom) and the standard process (top)

A stacked microLED architecture improves the performance, while also making the transfer process more productive. The company says that its design will offer a dramatic reduction in the production costs - especially the transfer process, which is reduced to a third (in terms of number of transfer steps), while also doing all the process from a single wafer.

Researchers from the Korea Advanced Institute of Science and Technology (KAIST) developed a new process that enables the fabrication of highly dense MicroLED displays - up to 63,500 PPI (!).

The technique involves stacking RGB LEDs in three dimensions and a semiconductor patterning process. Stacking LEDs one on top of the other creates color interference issues, and to overcome this the researchers deposited an insulating film between the layers. This also improved the efficiency of the microLED devices.