Here we demonstrate blade coated polymer light-emitting diodes (PLEDs) with different colors on a flexible substrate for optoelectronic sensor applications. Flexible electronics conform well to human body, which makes them favorable for wearable application. Blade coating is an attractive printing scheme to fabricate electronic devices, in that it is simple to configure and has high throughput. Here, surface energy patterning (SEP) is used to blade coat solution at desired areas. This technique reduces the amount of solution wasted through the sides of the blade, as compared to bladecoating without SEP, which leads to highly homogeneous active layer film and relatively consistent device performance. Using this technique, PLEDs with individual colors, red, green and near infrared (NIR) which are known colors that can be used to detect the condition of haemoglobin, are separately fabricated with blade coating. Luminous Efficacy and EQE of the PLEDs at 1Wsr-1m-2 were 42.7mW/W, 10% for Red, 31.2mW/W, 6.3% for Green, and 8.6mW/W, 3.1% for NIR. Also, SEP is further utilized to bladecoat two PLEDs with different colors on one substrate with no significant changes in the performance of the PLEDs. Before fabricating PLEDs for optoelectronic sensors we assessed design parameters such as minimum required flux and ideal distance between the light source and the detector using solid-state components. Based on the experiment, the PLEDs are fabricated to be used in conjunction with a photodiode to perform pulsating photoplethysmogram (PPG) measurements. Furthermore, with the multicolor PLEDs we successfully demonstrate oxygenation measurement.
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