Blue OLED-on-Silicon Sensor Detects Phosphorescence

Scientists at the Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP have developed a miniaturized phosphorescence sensor that combines marker and sensor on a small chip surface about the size of a thumbnail. OLED control and the sensor front-end are integrated into a silicon chip. The chemical marker is excited by modulated blue OLED light. The phosphorescent response of the marker is then detected directly inside the sensor chip. The marker determines the substance to be measured.

The miniaturized phosphorescence sensor combines a marker and sensor on a very small chip surface and could be produced at low cost in the long term. The first prototype of the sensor, which is currently designed for oxygen ratio monitoring, will be presented at embedded world 2019. Courtesy of Fraunhofer FEP.

The current sensor for exciting the oxygen-sensitive marker emits blue light in an area of approximately 4.7 by 2.2 mm. The decay time of the light emitted by the marker after excitation is a parameter of the oxygen concentration in the environment. The significantly lower phosphorescence signal is recorded via integrated silicon photodiodes, amplified locally in the chip and subsequently evaluated in relation to the excitation signal with regard to the phase shift. In the future, the researchers plan to reduce the size of the chip significantly, ultimately achieving a total chip size of less than 2 by 2 mm.

“Currently, the sensor is designed to detect changes in oxygen level. We have achieved functional verification of the component with this first setup, and can use the miniaturized sensor chip for oxygen measurements in gaseous environments,” said Karsten Fehse, project manager in the Organic Microelectronic Devices group. Fehse said that the researchers see the sensor chip as a platform for future developments such as the measurement of further parameters and deployment in other environmental conditions.

In the future, the sensor system will be further developed in the direction of multiparameter measurements. The researchers believe it could be applied to the monitoring and evaluation of cell cultures in small, disposable culture vessels and in bioreactors. It could also potentially be used to monitor liquids after the filling process in the pharmaceutical sector, in blister packs, and for quality control of oxygen-sensitive drugs.

The miniaturized phosphorescence sensor for oxygen measurement will be introduced at embedded world 2019, Feb. 26-28, in Nuremberg, Germany.