Fabrication of Flexible PDMS Films with Micro-Convex Structure for Light Extraction from Organic Light-Emitting Diodes.

In this study, we demonstrated organic light-emitting diodes (OLEDs) outcoupling with a flexible polydimethylsiloxane (PDMS) film with a micro-convex structure using the breath figure (BF) method. We can easily control the micro-convex pattern by adjusting the concentration of polystyrene and the humidity during the BF process. As process conditions to fabricate the micro-convex structure, polymer concentrations of 10, 20, 40, and 80 mg/mL and 60, 70, and 80% relative humidity were used. To evaluate the optical properties, we analyzed the transmission, diffusion, and electroluminescence with or without the micro-convex structure on the OLEDs. The shape and density of the micro-convex structure are related to its optical properties and outcoupling and we have experimentally demonstrated this. By applying a micro-convex structure, it achieved up to a 42% improvement in the external quantum efficiency compared to bare OLEDs (without any light extraction film). We expect the fabricated flexible light extraction film to be effective for outcoupling and applicable to flexible devices.

An Ultra-Compact MEMS Pirani Sensor for In-Situ Pressure Distribution Monitoring.

In this study, we designed a microelectromechanical system (MEMS) Pirani vacuum sensor with a compact size. Specifically, the sensor was successfully fabricated based on the Pirani principle and using a commercial eight-inch MEMS foundry process. The sensor fabrication process was carried out using only four photomasks and the proposed sensor had an ultra-compact fabricated size (<2.2 × 2.2 mm2). A vacuum measurement system was set up to comprehensively evaluate the fabricated sensors. The results demonstrated that the MEMS Pirani vacuum sensor has a high responsivity in the low-pressure domain from 100 Pa. The proposed sensor with a 953.0-Ω heater exhibited an average responsivity of 11.9 mV/Pa in the preferred range of 100 to 7 Pa and 96.0 mV/Pa in the range of 7 to 1 Pa. The sensor may be potentially suitable in many applications, such as vacuum indicators for processing equipment, health monitoring systems for social infrastructure, and medical and health applications.