Easy electrode fabrication method demonstrated for quantum dot light emitting diodes

Quantum dot light emitting diodes (QLEDs) offer tunable wavelengths and narrow emission widths, making them especially useful for display applications. However, contrary to QLEDs’ generally simple fabrication process, the manufacture of QLED top electrodes is difficult and costly. Using an indium, tin and bismuth alloy, Fengtian Xia and Shuming Chen demonstrated an easy and low-cost method to make QLED top electrodes.

To prepare the electrodes, Xia and Chen melted a mixture of 55% indium, 25% tin and 20% bismuth. They brushed the mixture to create a large film, which was cut into the appropriate size to place atop the QLEDs.

“The developed electrodes and vacuum-free fabrication process allow low-cost and high-throughput fabrication of devices for rapidly evaluating the performance of materials such as quantum dots or device structures,” said Chen.

In addition to eliminating the costly and time-consuming vacuum evaporation process typically required for electrode fabrication, the proposed technique improves the efficiency of the resulting QLEDs up to 50% for certain colors. Compared to the previously used metal laminates, the alloy allows itself to be processed and handled more easily while being less susceptible to temperature-dependent deformations.

The authors are working to identify additional benefits and functionalities of the material.

“Because the laminated low-melting-point alloy electrode is quite thick, we are currently investigating its possibility of serving as an encapsulation layer for the QLEDs for improving the lifetime,” Chen said.

Source: “Laminated low-melting-point-alloy electrodes for vacuum-free-processed quantum-dot light-emitting-diodes,” by Fengtian Xia and Shuming Chen, Applied Physics Letters (2020). The article can be accessed at https://doi.org/10.1063/5.0019188 .