An 8 $\times$ 8 Pixel Array Pen-Input OLED Screen Based on Organic Magnetoresistance

We present the design principles for a pen-input organic light-emitting diode (OLED) display based on the recently discovered organic magnetoresistance effect (OMAR). In the prototypical OLED material Alq
₃
, OMAR is as large as 10% for small magnetic fields, B=10 mT at room temperature. We construct a pen-input screen consisting of an 8 times 8 pixel OMAR array made from Alq
₃
, together with a magnetic pen that emits an ac magnetic field. We describe a multiplexed detection scheme that uses a single filter/amplifier circuit to sequentially scan the individual pixels for the presence of the magnetic pen. For this scheme to work efficiently, it requires using frequencies on the order of 100 kHz. We demonstrate that our OMAR devices can indeed follow such high frequencies under certain operating conditions