Bandwidth Dependency of (O)LEDs on Bias current

This work investigates the modulation bandwidth (Bmod) dependency of organic and non-organic light emitting diodes (OLED\LED) on the applied bias current (IB). The equivalent lumped element transient circuit models are shown with the critical components empirically extracted for both types of device. Four OLEDs of varying sizes are tested in addition to four high power LEDs (white phosphor, red, green and blue). Through analysis of the current-voltage characteristics, the device and dynamic diode resistances are determined as well as the ideality factors. We show that OLEDs have higher ideality factors to the traditional LEDs (almost double) hence the increased turn-on voltage, however have similar AC drive voltage characteristics across the emitting portion of the device between 8-12%. Furthermore, both devices exhibit an increase in Bmod with an increase in IB. It is shown that the OLEDs Bmod increases linearly in relation to IB, reaching =80% of the maximal Bmod at =60% of their maximum IB rating. Conversely, the LEDs display an exponential rise in Bmod in relation to IB, with =80% of the maximal Bmod at =35% of their maximum IB rating, with the red LED showing the greatest results at just 17%