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