CEA-Leti demonstrates combined microLED and organic photodetector architecture

CEA-Leti has demonstrated a co-packaged microLED and organic photodetector (OPD) architecture that enables optical sensing, integrating sensing capabilities directly into a microLED display without compromising display performance

The work, presented in the Photonics West paper titled ‘Co-Packaging of Organic Photodetector with MicroLED Matrix for Multifunctional Display Bio-Application’, validates a system-level approach combining device design, electronics, and modeling for multifunctional display applications.

MicroLEDs can provide high radiance using a limited fraction of the pixel surface, leaving space for additional functionality. Utilising this characteristic, CEA-Leti designed a microLED array co-packaged with a tailored OPD, with both devices optimised for operation at green wavelengths relevant to photoplethysmography (PPG) signal extraction.

To move past component-level demonstrations, the researchers created a dedicated electronic platform that enables full end-to-end characterisation of the entire signal chain, from microLED driving to the device under test to photodetection and readout circuitry.

Lock-in detection techniques were implemented to improve the signal-to-noise ratio and suppress static parasitic components. This is particularly relevant to biosensing detection, where the AC/DC ratio should be enhanced.

System validation was performed with optical phantoms engineered to replicate the absorption and scattering properties of biological tissue. This approach provided a controlled, repeatable environment for assessing biosensing performance under realistic conditions.

Experimental results were combined with analytical modelling to derive a closed-form expression linking microLED operating conditions, photodetector responsivity, and device-under-test reflectance to the detected signal. 

The co-packaged microLED devices demonstrated optical power up to 12mW at 525nm. On the detection side, OPD responsivity was tuned by adjusting the ZnPc active-layer thickness to match the microLED emission peak, yielding a responsivity of 0.083 A/W at the wavelength of interest.

The results revealed that microLED displays can support integrated optical sensing at the pixel level without sacrificing brightness, resolution, or sensing area. Unlike OLED-based approaches, where display and sensing functions compete for the same surface, this architecture enables both functions to coexist within the same front plane.

The fully characterised, end-to-end system establishes a technical foundation for displays that combine visual output with integrated sensing and adaptive functions, with potential relevance to next-generation displays. As opposed to relying on sensors in the display bezel, enabling sensing capabilities to be built directly into the display and made widespread.

Michaël Pelissier, lead author of the paper, said, “This work illustrates CEA-Leti’s system-technology co-design approach, from concept definition and microLED technology to photodetector co-design, electronics development, and experimental validation under realistic conditions. By combining hardware development with analytical modelling and simulation, we establish a concrete framework for evaluating and scaling sensing-integrated display architectures.”

The study established practical know-how for co-integrating microLED displays and optical sensing functions. The architecture is scalable and can be adapted to different pixel pitches and resolutions, depending on the targeted application, from medium-sized displays to larger formats.

The results provide a technical foundation for future multifunctional displays in which visual output and sensing capabilities are designed together at the system level.

This work is part of the IPCEI Microelectronics and Connectivity and was supported by the French Public Authorities within the framework of France 2030.