Analyzing and modulating energy transfer in ternary-emissive system of quantum dot light-emitting diodes towards efficient emission

Abstract

The mechanisms for energy transfer including Förster resonance energy transfer (FRET) and radiative energy transfer in ternary-emissive system consists of blended-quantum dots (QDs, red-QDs blended with blue-QDs) emissive layer (EML) and blue-emissive hole-transport material that contained in quantum dot light-emitting diodes (QLEDs) are complicated. As the energy transfer could exhibit either positive or negative impact on QD’s photoluminescence (PL) and electroluminescence (EL), it is important to analyze and modulate energy transfer in such ternary-emissive system to obtain high-efficiency QLEDs. In this work, we have demonstrated that proper B-QDs doping has a positive impact on R-QDs’ PL and EL, where these improvements were attributed to the B-QDs’ spacing effect on R-QDs which weakens homogeneous FRET among R-QDs and near 100% efficient heterogeneous FRET from B-QDs to R-QDs. With optimization based on the analysis of energy transfer, the PL quantum yield of blended-QDs (with R:B blending ratio of 90:10, in quality) film has been enhanced by 35% compared with that of unblended R-QDs film. Moreover, thanks to the spacing effect and high-efficiency FRET from B-QDs to R-QDs, the external quantum efficiency of QLEDs that integrate optimized blended-QDs (R:B=90:10) EML reaches 22.1%, which is 15% higher than that of the control sample (19.2%) with unblended R-QDs EML. This work provides a systematically analytical method to study the energy transfer in ternary-emissive system, and gives a valid reference for the analysis and development of the emerging QLEDs that with blended-QDs EML.

High Performance InP‐based Quantum Dot Light‐Emitting Diodes via the Suppression of Field‐Enhanced Electron Delocalization

“…The transfer efficiency due to coupling between delocalized excitons in adjacent QDs was defined as η dd = 1 − $$\frac{{{\rm{PL}}\,{\rm{lifetime}}\,{\rm{of}}\,{\rm{films}}\,{\rm{on}}\,{\rm{glass}}}}{{{\rm{PL}}\,{\rm{lifetime}}\,{\rm{in}}\,{\rm{solution}}}}$$. [ 7,42 ] Similarly, additional transfer efficiency due to the interaction between QDs and ZnMgO was defined as η dz = 1 − $$\frac{{{\rm{PL}}\,{\rm{lifetime}}\,{\rm{of}}\,{\rm{films}}\,{\rm{on}}\,{\rm{ZnMgO}}}}{{{\rm{PL}}\,{\rm{lifetime}}\,{\rm{of}}\,{\rm{films}}\,{\rm{on}}\,{\rm{glass}}}}$$. Transfer efficiency characterized the impacts of the exciton or charge transfer on the PL decay dynamics.…”

“…The transfer efficiency due to coupling between delocalized excitons in adjacent QDs was defined as η dd = 1 − PL lifetime of filmson glass PL lifetime in solution . [7,42] Similarly, additional transfer efficiency due to the interaction between QDs and ZnMgO was defined as η dz = 1 − PL lifetime of filmson ZnMgO PL lifetime of filmson glass . Transfer efficiency characterized the impacts of the exciton or charge transfer on the PL decay dynamics.…”

High Quantum Yield Blue InP/ZnS/ZnS Quantum Dots Based on Bromine Passivation for Efficient Blue Light‐Emitting Diodes

“…This redshift could be attributed to the quantum-confined Stark effect [25] and homogeneous Förster resonant energy transfer in close-packed QDs film (Figure S11, Supporting Information). [26,27] The photographs of QLED device working under 6 V bias are provided as the insets of Figure 6b.…”