Scientists Create Optical Nanocavity Increasing Light Absorption

6 March 2014
Scientists from the University of Buffalo (UB), helped by colleagues from two Chinese universities, have developed an optical "nanocavity" that could help increase the amount of light absorbed by ultrathin semiconductors. The advancement could lead to the creation of more powerful photovoltaic cells and improvements in video cameras and even hydrogen fuel, as the technology could aid the splitting of water using energy from light.
Ultrathin semiconductors are increasingly used in modern electronics, but their main flaw is that they cannot absorb light as well as conventional semiconductors. Researchers at Harvard University have been successful in similar research by integrating thin films of germanium, a common semiconductor, on a gold surface. However, gold is a material that is very expensive to use, said Suhua Jiang, associate professor of materials science at Fudan University in China. His team instead used less costly materials, including aluminum, aluminum oxide and germanium, to boost the amount of light absorbed by semiconductors.
The team demonstrated light passing through the germanium, which is 1.5 to 3 nanometers thick, and circulating in a closed path through the aluminum oxide and aluminum. The light absorption rate achieved was 90%, with germanium absorbing approximately 80% and aluminum accounting for the rest.
The rates were very strong because the larger amount of light remains within the semiconducting material, commented Haomin Song, PhD candidate in electrical engineering at UB.
The findings from the study, published in the journal Advanced Materials, suggest that nanocavity has very promising potential that could be a springboard for major breakthroughs in energy-harvesting and conversion, security and other areas that will be beneficial to humankind, lead author Qiaoqiang Gan said.