Materials for solar cells could power instruments in space

Researchers in Arkansas are investigating the use of semiconductor materials in photovoltaic devices that power satellites and other instruments in space.

Experts in Dr Omar Manasreh’s Optoelectronics Research Lab at the University of Arkansas will use funding from NASA and the university to continue growing and functionalising semiconductor and metallic nanoparticles to be used in solar cells.

The ultimate goal is to fabricate and test a photovoltaic device that is capable of possessing a solar-energy conversion efficiency of 40 per cent or better.

Currently, solar panels used on NASA satellites and spacecraft use silicon-based technology, which cannot produce light-to-energy conversion efficiency greater than 23 per cent.

Manasreh, a professor of electrical engineering at the University of Arkansas, is said to employ two approaches to fabricate solar cells. Instead of silicon, the first approach involves a combination of copper, indium, gallium and selenium (CuInSe2 and CuInGaSe2) as the semiconductor material to grow nanocrystals.

The researchers make the nanocrystals functional by generating volatile ligands, which are molecules that bind to a central atom.

The nanocrystals are then either converted into thin films or combined with titanium-dioxide or zinc-oxide nanotubes to create the desired solar cells. After fabrication of the cells, the researchers will test and evaluate their performance.

The second approach uses molecular beam epitaxy, a method of depositing nanocrystals, to create quantum dots made of indium arsenide (InAs).

To enhance the performance of the solar cells, the researchers will use short ligands to couple metallic nanoparticles to the nanocrystals and quantum dots.

They will then investigate the plasmonic effect of trapping sunlight, which in turn increases the energy-conversion efficiency.