Decoupling the Conductivity–Fluorescence Tradeoff of SnO₂ Nanocrystals for Efficient and Stable Quantum Dot Light‐Emitting Diodes

Abstract Electron‐transporting layers (ETLs) assembled from SnO 2 nanocrystals show promise in addressing the stability issues faced by solution‐processed quantum dot light‐emitting diodes (QLEDs). However, the electrical conductivity of SnO 2 nanocrystals bottlenecks QLED performance, and efforts to achieve effective n‐type doping are constrained by dopant availability and charge‐induced exciton quenching. In response, Sb‐doped SnO 2 nanocrystals with doping concentrations less than 1 mol% are explored, a range overlooked in previous research, and the ETL is designed accordingly. Comprehensive characterizations reveal that 0.45 mol% Sb doping transitions the electrical conduction from trap‐limited to trap‐free space‐charge‐limited, and 0.84 mol% doping results in Ohmic conduction, along with a 100‐fold conductivity enhancement. Meanwhile, trap‐filling mitigates the fluorescence quenching of the colloidal quantum dots, with significant increases only observed when doping concentrations exceed 0.45 mol%. Drawing inspiration from these findings, a SnO 2 ETL with gradient Sb doping levels for QLEDs to decouple the conductivity–fluorescence tradeoff is developed. Consequently, this ZnO‐free QLED significantly outperforms comparable devices, achieving a luminance of 2.8 × 10 5 cd m −2 , an external quantum efficiency of 18.3%, and a T 95 operational lifetime of 4320 h at 1000 cd m −2 , all while showing no signs of positive aging.