Stabilizing Perovskite LEDs

Abstract

One of the largest obstacles that perovskite LEDs (PeLEDs) face is achieving emission stability similar to OLEDs and inorganic LEDs. Two mechanisms of device degradation are the focus of this project. The first is the migration of ions from the perovskite layer, specifically the iodide in methylammonium lead iodide (MAPbI3). Ions can migrate across the device and interact with the other layers causing changes at interfaces and modifying energy levels. This is more prevalent in top-emitting PeLEDs where a reflective metal anode is required. Various thicknesses of alumina (Al2O3) in a bottom-emitting PeLED with a similar structure to a top-emitting PeLED are investigated to test potential blocking of iodide migration via emission stability. Ultimately, this layer did not perform as hypothesized due to the increased resistance of the alumina. Joule heating is another phenomenon known to cause degradation of perovskite LEDs. Temperature and ion migration are closely linked, which opens up less invasive methods of countering device degradation. Devices fabricated on silicon substrates are compared to those fabricated on glass substrates. Only top-emitting devices can be used for comparing silicon versus glass due to silicon’s opaqueness. Although the IV and stability data only allowed for limited conclusions, thermal images directly proved that devices deposited on silicon substrates dissipated heat more effectively.