Abstract:We have proposed a novel concept of a pressure sensor called electroluminescent pressure sensor (ELPS) based on oxygen quenching of electroluminescence. The sensor was fabricated as an organic light-emitting device (OLED) with phosphorescent dyes whose phosphorescence can be quenched by oxygen molecules, and with a polymer electrode which permeates oxygen molecules. The sensor was a single-layer OLED with Platinum (II) octaethylporphine (PtOEP) doped into poly(vinylcarbazole) (PVK) as an oxygen sensitive emissive layer and poly(3,4-ethylenedioxythiophene) mixed with poly(styrenesulfonate) (PEDOT:PSS) as an oxygen permeating polymer anode. The pressure sensitivity of the fabricated ELPS sample was equivalent to that of the sensor excited by an illumination light source. Moreover, the pressure sensitivity of the sensor is equivalent to that of conventional pressure-sensitive paint (PSP), which is an optical pressure sensor based on photoluminescence.

Pressure-sensitive paints (PSP) and pressure-sensitive molecular film (PSMF) are drawing much attention, since the techniques enable us to measure pressure/oxygen concentration distribution with high spatial resolution. A measurement system of PSP/PSMF is generally composed of a sensor layer (PSP/PSMF itself), an illumination light source, a photo-detector, and optics such as optical filters and mirrors. Since dye molecules in a sensor layer are photo-excited by an illumination light, the measurement system needs optical windows to transmit UV light for the illumination light and needs an optical filter to eliminate the illumination light, which also reduces the luminescence detected by a photo-detector. We have proposed a novel concept of a pressure sensor called electroluminescent pressure/oxygen sensor (ELPS/ELOS) based on oxygen quenching of electroluminescence without an external illumination light source. The sensor was fabricated as an organic light-emitting device (OLED) with phosphorescent dyes whose phosphorescence can be quenched by oxygen molecules, and with a polymer electrode which permeates oxygen molecules. The pressure sensitivity of the fabricated ELPS sample was equivalent to that of the sensor excited by an illumination light source. Moreover, the pressure sensitivity of the sensor is comparable to that of conventional PSP.