High-efficiency quantum dot light-emitting diodes based on Li-doped TiO₂ nanoparticles as an alternative electron transport layer

Abstract

We report high-efficiency quantum dot light-emitting diodes (QLEDs) with Li-doped TiO₂ nanoparticles (NPs) as an alternative electron transport layer (ETL). Colloidally stable TiO₂ NPs are applied as ETLs of inverted structured QLEDs and the effect of the addition of lithium (Li) to TiO₂ NPs on device characteristics is studied in detail. Compared to pristine TiO₂ NPs, Li-doped ones are found to be beneficial for the charge balance in the emitting layer of QLEDs mainly by means of their upshifted conduction band minimum, which in turn limits electron injection. A green QLED with 5% Li-doped TiO₂ NPs produces a maximum luminance of 169 790 cd m^-2, an EQE of 10.27%, and a current efficiency of 40.97 cd A^-1, which indicate the best device performances to date among QLEDs with non-ZnO inorganic ETLs. These results indicate that Li-doped TiO₂ NPs show great promise for use as a solution-based inorganic ETL for future QLEDs.