Dan Dong

Highly Conductive and Uniform Alginate/Silver Nanowire Composite Transparent Electrode by Room Temperature Solution Processing for Organic Light Emitting Diode

A novel transparent electrode composed of alginate/silver nanowire (AgNW) with high conductivity and low roughness is fabricated via a solution process at room temperature. The sol-gel transition of the alginate triggered by CaCl2 solution bonds the AgNWs to the substrate tightly. Meanwhile, Cl- in the solution can renovate the cracks on the AgNW surfaces created during the mechanical pressing, resulting in a great increase of the electrical conductivity. The alginate/AgNW composite film can reach a sheet resistance of 2.3 Ω/sq with a transmittance of 83% at 550 nm. The conductivity of the composite film remains stable after bending and tape tests, demonstrating excellent flexibility and great adhesion of AgNWs to the substrate. Moreover, the composite film shows better stability to resist longtime storage than conventional annealed-AgNW film. The organic light emitting diode using such alginate/AgNW composite film as anode presents current densities and luminances comparable to those of indium tin oxide (ITO) anode, and higher efficiencies are obtained due to the better charge balance.

Enhanced performances of quantum dot light-emitting diodes with doped emitting layers by manipulating the charge carrier balance

High performance quantum dot light-emitting diodes (QD-LEDs) have been realized by doping quantum dots into a polymer matrix as an emitting layer (EML). Efficient energy transfer from the matrix to QDs occurs, resulting in high efficiency QD emission. The issue of hole injection from the hole transport layer to the QD layer, which occurs in normal QD-LEDs due to the ultra-low highest occupied molecular orbital (HOMO) level of QDs, can be neglected. By introducing an additional hole blocking layer with a suitable lowest unoccupied molecular orbital (LUMO) level and electron mobility between the doped QD EML and electron transporting layer (ETL), the emission from the ETL can be eliminated, and an external quantum efficiency (EQE) of 4.7% has been obtained.

Highly robust and ultrasmooth copper nanowire electrode by one-step coating for organic light-emitting diodes

A novel copper nanowire (CuNW)/chitosan composite transparent electrode is fabricated via a simple one-step solution process in ambient air, and the resulting film shows high electrical conductivity and air stability, low surface roughness and enhanced transmittance. After coating with chitosan dissolved in L-ascorbic acid solution, the copper oxide layer on the surface of pristine CuNW reacts with L-ascorbic acid and is reduced to metal copper. Meanwhile, under the effective protection of chitosan, CuNWs are welded well by thermal annealing in air, resulting in relatively low sheet resistance of 19 Ω sq−1 with transmittance of 81%. The chitosan fills the gaps between nanowires, and the nanostructure becomes more uniform, resulting in low root mean square (RMS) of 6.2 nm and enhancement in transmittance. This CuNW composite film can resist water/ethanol immersion and an aging test at 120 °C on a hot plate in air environment without clear conductivity deterioration. Since the film can be easily removed by an acid–base solution, it allows a feasible patterning process. After employing this film as the anode in an OLED device, the device shows higher performance than the device based on an ITO anode.