Optimization of Stacked Inverted Top-Emitting Organic Light-Emitting Diodes

Organic light-emitting diodes (OLEDs) are light sources that use a thin film of organic materials as the light-emitting component. OLEDs show much promise as a technology for thin, lightweight, and flexible displays and lighting panels. Conventional OLEDs are formed from an electrolumeniscent organic thin film used as an emissive layer located between a bottom-anode and a top-cathode all on top of a substrate. They are generally bottom-emitting, such that the light is emitted from the bottom through a transparent contact such as indium tin oxide. However, OLEDs can also be top-emitting such that the light is emitted through a semi-transparent top-electrode, allowing them to be deposited on opaque substrates. In addition, an inflexible indium tin oxide contact is no longer needed, allowing for flexible devices. In an inverted OLED, the electrode positions are switched, with the anode on top and the cathode on bottom, making inverted OLEDs more conveniently incorporated into active-matrix displays which use superior n-type driving technology.  Here,  stacked inverted top-emitting OLEDs are fabricated and optimized. Stacked OLEDs are devices in which a series of emissive units are stacked on top of one another with a charge-generating layer in between, allowing more light to be produced at lower current densities, resulting in longer lifetimes. The OLEDs reported are developed in lab through vacuum thermal evaporation and characterized using a sourcemeter, calibrated photodiode, and spectrometer. Specifically, the effects of varying layer properties such as Al and LiF interlayer thicknesses are reported.