Nanotextured Organic Light Emitting Diode Based Chemical Sensor

In this paper we present the design, fabrication and development of an optical, label free chemical sensor technology based on the portable lab-on-a-chip format. This sensor technology employs the use of nanotextured thin film surfaces packaged in a stacked vertical array format functioning as organic light emitting diodes (OLED's). The intensity of emitted light from OLED's is modulated as a function of the analyte concentration. The OLEDs were fabricated in a layer by layer configuration with an indium tin oxide anode and an aluminum cathode and TPD as a hole transport layer and AlQ(3) as an electron transport layer. ITO/TPD/AlQ(3)/Al sandwich OLEDs were converted into sensors by converting the cathode (Al) surface into an active sensing area. The prototype sensor performance was evaluated in the detection of two aliphatic hydrocarbons-ethanol and methanol. The detection sensitivity was found to be in the lower parts per million (ppm). The limit of detection for ethanol was 1 ppm and that for methanol was 10 ppm. Chemical detection was achieved upon the comparison of turn-on voltages and the intensities of the output light from the OLED when chemical was being injected onto the cathode surface, with that of a standard OLED turn-on voltage and intensity. The modulation in these two parameters with respect to the standard was determined as a measure of detection of the two chemical species.