Tandem organic semiconductor devices for optical sensor application

Abstract

Organic optical sensors compose of vertically integrated organic photodetector (OPD) and organic light-emitting diode (OLED) have been demonstrated. The stripe-shaped cathode is used in the OLED components to create light signals, while the space between the stripe-shaped cathodes serves as the detection window for integrated OPD units. A transitional meal oxide/silver bi-layer inter-electrode is adopted to connect vertically the OLED and OPD units, serving simultaneously as the cathode for the front OLED and an anode for the upper OPD units in the sensor. In the stacked organic semiconductor devices, the emission of the OLED units is confined by the area of the opaque stripe-shaped cathodes, optimized to maximize the reflected light passing through the window space for detection by the OPD components. This can ensure high OLED emission output, increasing the signal/noise ratio. The performance of the functional organic sensors was analyzed, relating to the optimization of light coupling between the OLED and OPD components, as well as the examination of the optical and frequency responses. It reveals that the organic sensors are capable of signal processing in the 10 kHz regime. The design and fabrication flexibility provided by the material and process could readily construct multilayered organic sensor arrays for application in wearable units, disposable point of diagnosing, low cost bioassay devices, lab-on-chip, and vital sign monitoring and compact information systems.