Spectroscopic insights into the performance of quantum dot light-emitting diodes

Lighting consumes almost one-fifth of all electricity generated today. In principle, with more efficient light sources replacing incandescent lamps, this demand can be reduced at least twofold. A dramatic improvement in lighting efficiency is possible by replacing traditional incandescent bulbs with light-emitting diodes (LEDs) in which current is directly converted into photons via the process of electroluminescence. The focus of this article is on the emerging technology of LEDs that use solution-processed semiconductor quantum dots (QDs) as light emitters. QDs are nano-sized semiconductor particles whose emission color can be tuned by simply changing their dimensions. They feature near-unity emission quantum yields and narrow emission bands, which result in excellent color purity. Here, we review spectroscopic studies of QDs that address the problem of nonradiative carrier losses in QD-LEDs and approaches for its mitigation via the appropriate design of QD emitters. An important conclusion of our studies is that the realization of high-performance LEDs might require a new generation of QDs that in addition to being efficient single-exciton emitters would also show high emission efficiency in the multicarrier regime.