Unraveling the Energy Transfer Mechanisms in Bi‐Color and Tri‐Color Quantum Dots: toward Efficient White Quantum Dot Light‐Emitting Diodes

Abstract One of the considerable effects that limit the performance of white quantum dot (QD) light‐emitting diodes (W‐QLEDs) is the Förster resonance energy transfer (FRET) among different colored QDs. Here, the FRET mechanisms among QDs are unraveled and how FRET affects the performance of W‐QLEDs is disclosed. The results show that although FRET is beneficial for harvesting the energy of nonradiative excitons, it is unhelpful for the improvement of the total emission quantum yield of bi‐color or tri‐color QDs. Due to the existence of FRET, a large proportion of blue QDs should be incorporated to obtain a balanced white emission, which remarkably deteriorates the efficiency of the white emission. With the developed device structure, the FRET among QDs can be suppressed, and thus, the external quantum efficiency (power efficiency) of the W‐QLEDs is improved from 9.31% to 27.03% (12.18–25.52 lm W⁻¹), representing an improvement factor of 2.9 (2.1) compared with that of the conventional W‐QLEDs. The results not only deepen the insight into the FRET mechanisms among QDs but also provide solutions and inspirations for the future development of efficient W‐QLEDs.