Simultaneous mobility reduction and conductivity enhancement of SnO2 nanoparticles via fluorine doping for balanced charge transport in high-performance quantum dot light-emitting diodes

Quantum-sized SnO2 nanoparticles (NPs) have emerged as a promising electron transport layer (ETL) in solution-processed quantum dot light-emitting diodes (QLEDs) due to their high chemical stability and excellent optical transparency. However, the intrinsically high electron mobility of SnO2 tends to cause excessive electron injection and charge transport imbalance, ultimately compromising the efficiency and operational stability of QLED devices. To address this issue, we propose an n-type fluorine-doping strategy for SnO2 NPs that simultaneously tailors both electron mobility and electrical conductivity. This approach effectively lowers the electron mobility of the SnO2 NPs to better match the hole mobility of the hole transport layer (HTL), while simultaneously enhancing electrical conductivity to promote efficient electron injection. The resulting more balanced charge transport within the QLED leads to significantly improved overall device performance. As a result, the red-emitting inverted QLED device based on 10 at% F-doped SnO2 NPs exhibits outstanding performance, achieving a maximum luminance of 129 117 cd m−2, a peak external quantum efficiency (EQE) of 16.55% and a turn-on voltage (Von) of 2.4 V.