Facile Synthesis of Multicolored Stacked Quantum Dot Films for Efficient White Light Emission

Abstract

Quantum dot (QD)-based white light-emitting diodes (LEDs)or whiteQD-LEDs were successfully fabricated by stacking QD films of primarycolors (i.e., red, green, and blue). An ultrathin ZnO film was depositedbetween each QD layer to facilitate the formation of a tricolor-stackedQD structure. Such stacked QD films effectively suppress the Fo''rsterresonance energy transfer between QDs and enable efficient blue lightemission, unlike randomly mixed QD films of different colors. Thephotoluminescence (PL) spectra of various QD films were obtained tostudy the change in the corresponding color gamut with applied voltage.In addition, QD-LEDs were fabricated based on the PL behavior andelectronic band diagrams of QDs of different colors. Maximum luminanceand peak EQE of white QD-LED shows 5700 cd/m(2) and 1.1%compared to 2200 cd/m(2) and 0.3% of QD-LED with mixed QDlayer. Finally, a smooth color transition and white light emissionwere achieved using a blue/green/red stacking sequence for the QDs,which successfully suppressed the energy transfer effect. The overallperformance and brightness of the white QD-LEDs synthesized in thisstudy can be further enhanced by developing high-performance blueQDs.