Tailoring Electron Mobility and Conductivity of SnO ₂ Nanoparticles via Mg Doping for High-Performance Quantum Dot Light-Emitting Diodes

Quantum-sized SnO₂ nanoparticles have emerged as a promising electron transport layer (ETL) in quantum dot light-emitting diodes (QLEDs) due to their high chemical stability, wide bandgap, and high electron mobility. However, their excessive electron mobility often leads to charge transport imbalance, thereby limiting the device performance. Herein, we report a p-type doping strategy using Mg²⁺ ions to modulate the electron transport capability of SnO₂ nanocrystals. By varying Mg-doping concentration, we achieve a wide-range tuning of electron mobility and conductivity over nearly 3 orders of magnitude. This suppression of electron transport enables the balanced charge injection in inverted QLEDs. As a result, red-emitting devices incorporating 2.0% Mg-doped SnO₂ ETLs exhibit an average external quantum efficiency (EQE) of 19.35% and a peak EQE of 22.04%. This work demonstrates Mg-doped SnO₂ nanoparticles as a superior alternative to ZnO nanoparticles for highly efficient and stable QLEDs.