Abstract:
In this report, the development of flexible OLED-based (organic light-emitting diodes) light
emitter and detector array is discussed for low-cost colourimetric analysis of water samples.
LEDs have been used as optical sensors by measuring their discharge time, when exposed
to different light intensities. This report investigates whether an LED emitter and detector
array, with different colour LEDs and therefore wavelengths, can be used for colourimetric
analysis (specifically a colourimetric pH test).
This report also investigates whether flexible OLEDs can be used to create a similar light
emission and detection array as the LED array. The flexibility and inkjet printability of
OLEDs make it desirable for lab-on-chip, microfluidic, rapid diagnostic devices, which is agrowing field of research. Using OLEDs as light detectors is a novel concept; therefore
OLED panels were characterized as light detecting devices in this report in terms of
wavelength sensitivities, angular response, emission spectra, discharge time, photocurrent,
capacitance, and resistance. These results were compared to the results of an LED, used as a
light detector. A discrete model of the OLED was also simulated in SPICE software.
The manufacturing of OLEDs was also investigated. Printed electronics is a growing
additive manufacturing technique that is capable of printing small, low-cost, printed
electronic devices on flexible substrates. Inkjet printed electronics is of special interest as
there is little material wastage and high resolutions are attainable. Flexible OLEDs have been
manufactured using a combination of screen printing, inkjet printing, and nano-printing
techniques. In this report, an investigation was done on whether a fully inkjet printed OLED
can be manufactured. A fully inkjet printable OLED structure was simulated, and the layers
of the OLED structure and layer thicknesses were then optimized to maximize the number
of photons that exit the device.
