Remarkable lifetime improvement of quantum-dot light emitting diodes by incorporating rubidium carbonate in metal-oxide electron transport layers

Abstract

Despite the immense research on quantum dot light emitting diodes (QLEDs), there are still some challenges for QLEDs such as improvements of efficiency roll-off at high luminance and poor lifetime. Here, we demonstrated a remarkable improvement of the efficiency roll-off and operational lifetime in inverted, red quantum dot light emitting diodes (R-QLEDs) by incorporating rubidium carbonate (Rb₂CO₃) into the Mg doped ZnO (MZO) electron transporting layer (ETL). The optimum Rb₂CO₃ doping concentration and thickness for the ETL are found to be 4% and 90 nm, respectively. The R-QLED with the 90 nm Rb₂CO₃ doped MZO ETL with 4% doping shows a long operational lifetime (T₉₀) of 14 672 h at the initial luminance of 100 cd m⁻², a maximum luminance of 129 100 cd m⁻² and a high current efficiency (CE) of 13.6 cd A⁻¹ at a high luminance of 60 000 cd m⁻². These improvements appear to be due to the fact that Rb₂CO₃ acts as a strong n-type dopant and enhances the thermal stability of MZO according to various thin-film analyses.