Water-induced high-performance quantum-dot light-emitting diodes

Solution-processed light-emitting diodes (LEDs) are appealing for their potential in the low-cost fabrication of large-area devices. However, the limited performance of solution-processed blue LEDs, particularly their short operation lifetime, is hindering their practical use in display technologies. Here we demonstrate that trace water in the device—previously considered detrimental to most solution-processed LEDs—dramatically enhances the performance of quantum-dot LEDs. This breakthrough stems from our comprehensive mechanism investigations into the positive aging phenomenon, a long-standing puzzle in the quantum-dot LED field. Our findings reveal that water passivation on the surface of electron-transporting layers, which are composed of zinc-oxide-based nanoparticles, improves charge transport and enhances exciton radiative recombination by suppressing hole leakage during device operation. Combined with the advanced top-emitting architecture, our blue quantum-dot LEDs achieve a high current efficiency of 37.1 cd A −1 , a blue index (colour-coordinate-corrected current efficiency) of over 490 cd A −1 \({{\rm{CIE}}}_{y}^{-1}\) and unprecedented stability, with an extrapolated T 95 lifetime (at an initial brightness of 1,000 cd m −2 ) of 287 h. Our work may inspire further exploration into surface passivation of nanocrystalline functional layers, critical for the advancement of emerging solution-processed optoelectronic and electronic devices.