Exploring the emission mechanism of dichromatic white-light quantum-dot light-emitting diodes using wavelength-resolved transient electroluminescence analysis.

Exploring electroluminescence (EL) processes is extremely vital to fabricate efficient white-light quantum-dot light-emitting diodes (QLEDs). A model white QLED consisting of a bilayer CdSe/ZnSeS quantum-dot (QD)//CuInS2/ZnS QDs emissive layer has been used to analyze the white-light emission mechanism. In this design, the CdSe/ZnSeS QDs and CuInS2/ZnS QDs contribute to the blue and yellow emissions, respectively, in the dichromatic white QLED. Wavelength-resolved transient EL (TrEL) results demonstrate that the excitons are mainly formed on the CuInS2/ZnS QDs in the QLED operated at low biases due to the low barrier to hole injection and energy transfer from the CdSe/ZnSeS QDs to the CuInS2/ZnS QDs. Further, the TrEL decays of both white and monochromic devices reveal that the emission behavior of the white QLED is closely related to that of the monochromic device, but is minimally affected by the interactions between different emission units. The simulation results performed by the solar cell capacitance simulator model agree well with the experimental data. Our results show an insight into the EL processes in the white device QLED and demonstrate a powerful tool to investigate emission behavior of the white QLEDs.