Technology to cut electron sources cost discovered

Rice University has announced that its engineers have discovered technology that could lower the cost of semiconductor electron sources.

The electron sources are essential components in devices such as low-light cameras, night-vision goggles, particle accelerators and electron microscopes.

The Houston, Texas-based university’s researchers and collaborators at Los Alamos National Laboratory (LANL) describe in a Nature Communications paper the first process for making electron sources from halide perovskite thin films, which efficiently convert light into free electrons.

US Department of Energy national laboratory LANL was initially organized during World War II for the design of nuclear weapons as part of the Manhattan Project. Nature Communications is a peer-reviewed, open access, scientific journal published by Nature Research.

Manufacturers have been paying billions for photocathode electron sources that are made from semiconductors containing rare elements like selenium, gallium, tellurium and cadmium.

Aditya Mohite, a Rice materials scientist and chemical engineer and the study’s co-corresponding author, stated, “This should be orders of magnitude lower in cost than what exists today in the market,” adding the halide perovskites can outperform present semiconductor electron sources in many ways.

“First, there’s the combination of quantum efficiency and lifetime,” he said. “Even through this was a proof-of-concept, and the first demonstration of halide perovskites as electron sources, quantum efficiency was only about four times lower than that of commercially available gallium arsenide photocathodes. And we found halide perovskites had a longer lifetime than gallium arsenide.”

One more edge that perovskite photocathodes have comes from how they are made — the inexpensive way of spin coating, which can easily be scaled up, said Mohite.

Quantum efficiency represents the effectiveness of a photocathode at converting light to usable electrons.

Fangze Liu, a postdoctoral research associate at LANL and the study’s lead author, said, “If each incoming photon generates an electron and you collected every electron, you would have 100% quantum efficiency.”

He added, “The best semiconductor photocathodes today have quantum efficiencies around 10-20%, and they are all made of extremely expensive materials using complex fabrication processes. Metals are also sometimes used as electron sources, and the quantum efficiency of copper is very small, about .01%, but it’s still used, and it’s a practical technology.”

There are two ways that halide perovskite photocathodes would bring cost savings. First, the raw materials required to make them are plenty and cheap, and the second, the manufacturing process is cheaper and easier compared to that of conventional semiconductors.