Van der Waals Epitaxy of Thin Gold Films on 2D Material Surfaces for Transparent Electrodes: All-Solution-Processed Quantum Dot Light-Emitting Diodes on Flexible Substrates.

With the assistance of van der Waals (vdW) epitaxy, nanometer-thick and highly conductive gold films are deposited onto MoS 2 surfaces for use as transparent anode electrodes in quantum dot light-emitting diodes (QLEDs) on poly(ethylene terephthalate) (PET) substrates. After transferring wafer-scale and monolayer MoS 2 to PET substrates, 10 nm thick gold (Au) films are deposited onto the two-dimensional (2D) material surfaces as anode electrodes. Bounded only by weak vdW forces on 2D material surfaces, the diffusive Au adatoms tend to facilitate lateral growth and lead to the formation of continuous and highly conductive thin metal films in the nanometer regime. The Au film exhibits excellent tensile bending stability for its sheet resistance, which is superior to that of rigid indium-tin oxide (ITO) films on PET substrates. Thermally stable CdSe@CdZnS/ZnS QLEDs are fabricated on the PET substrate. Compared with devices fabricated on sapphire substrates, the phenomenon of sub-bandgap turn-on is observed for the flexible device. Based on our demonstrations, the high conductivity and robust durability toward substrate bending make the nanometer-thick Au film grown on 2D material surfaces a promising candidate to replace current ITO anode electrodes for flexible device applications.