Effect of Caesium Based Compounds As Electron Injection Layer In Fluorescent Polymer Organic Light-Emitting Diode

Electron transport in light emitting semiconducting polymers is often limited by traps. By studying the role of Caesium carbonate (Cs₂CO₃), Caesium Nitride (CsN₃), Caesium Fluoride (CsF) are chosen as the electron injection layer, it is discovered that CsF has the ability to reduce the electron traps followed by CsN₃ and then Cs₂CO₃ with trap density of 1.5 x 10¹⁸ cm^-3 , 2.22 x 10¹⁸ cm^-3 , 3.03 x 10¹⁸ cm^-3 , respectively. We also found out that for such materials, charge balance as often obtained from comparison between electron and hole only devices, is not a good predictor for current efficiency. In fact, highest efficiency is obtained using Cs₂CO₃ with 11.9 lm/W for superyellow poly-(p-phenylenevinylene) at 1000 cdm^-2.