Synthesis of percolative ZnO quantum-dot superlattices

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We have studied percolative (P-) quantum-dot superlattices (QDSLs) based on the percolation threshold for the formation of QDSLs that are suitable for solution-based fabrication processes. Cross-sectional transmission-electron-microscope measurements revealed the presence of ZnO cores with a mean radius of 2.5 nm that were densely and nearly mono-dispersed in the printed emission layer (EML). Elemental analysis indicated the presence of Mg elements locally around the ZnO cores, suggesting the formation of MgO shells. The blue shifts observed in the transmittance and photoluminescence spectra indicated band gap widening induced by quantum confinement effects. From analysis of the current versus voltage and current versus light intensity characteristics, the formation of the percolative current paths was indicated. Consequently, the structural and optical studies of the EML and the device performance of the light-emitting device demonstrate that the formation of P-QDSLs is possible.