Modeling Current–Voltage Characteristics of Bilayer Organic Light-Emitting Diodes

Electrical characteristics of bilayer organic light-emitting diodes (OLEDs) are analytically modeled based on a band diagram analysis. Two working regions, a low-injection (LI) region and a high-injection (HI) region, are proposed for operations of a general heterolayer OLED according to numerical solutions of OLED equations. Under the LI case, a diffusion-based current-voltage formulation is developed, with significant impacts from defect states. For HI operations, a drift-based current-voltage relationship is formulated incorporating the field-dependent carrier mobility of amorphous materials. The models' validity is demonstrated on the measured data of fabricated OLEDs.