In a recent article published in Nanotechnology [22 125705 (2011)], researchers from Shanghai Jiao Tong University, China, and Boston College, US, have reported a thorough theoretical study of the light absorption in single c-Si/a-Si coaxial nanowires. The team has made great progress in establishing the fundamental mechanism of light absorption in c-Si/a-Si coaxial nanowires. In addition, the group found the geometrical optimum condition for coaxial nanowires, which provides efficient energy absorption while retaining excellent charge collection.

"We've obtained an increase in photocurrent of up to 560% in coaxial nanowires compared with silicon nanowires. It is beautiful that this happens when the a-Si shell thickness is equal to the c-Si core diameter." Mr W F Liu, the first author of the article, told nanotechweb.org.

Stepping-stone device

In addition, the group showed how to obtain a further increase in photocurrent (up to 60%) by coating nonabsorbing dielectric SiO2 shells on the coaxial nanowires (see schematic view). "These super-hybrid c-Si (core)/a-Si (inner shell)/SiO2 (outer shell) coaxial nanowires were considered in related work, and we believe they serve as a stepping stone to developing highly efficient integrated power sources to drive nanoelectronic devices." added Dr J I Oh, a co-author of the study.

Prof. Shen, who leads the team, revealed that the group is developing a prototype coaxial nanowire photovoltaic cell, which he hopes will complete the story of coaxial nanowires for photovoltaic applications.