A comprehensive EL testing approach for the leading MicroLED manufacturing methods

To establish microLEDs as a viable alternative, their production cost must be significantly reduced—primarily by minimizing microLED size. However, this size reduction often results in a substantial drop in external quantum efficiency (EQE). While numerous studies have addressed this challenge and gradually improved microLED efficiency, functional testing—specifically electroluminescence (EL) testing—throughout the production process can be a powerful tool. It provides deeper insights and accelerates the development cycle. For scalable manufacturing, high-speed, non-destructive testing is essential. We demonstrate that conventional non-invasive methods such as automated optical inspection (AOI) or photoluminescence (PL) often yield incomplete or misleading results, making EL testing indispensable. This paper presents a high-throughput, damage-free EL testing method using patented “soft-touch” probes. MicroLED display fabrication typically follows one of three approaches: mass transfer, monolithic integration (microdisplays), or nanowire growth. Each approach involves distinct process steps and challenges, requiring tailored testing strategies. We discuss the critical stages in each approach where EL testing is most impactful and how it can be effectively implemented.