Jun Xu and his team from the Oak Ridge National Laboratory have just created a three-dimensional “nanocone-based solar cell platform,” which is able to increase the light conversion efficiency by almost 80 percent by eliminating the issue of poor charge transport due to bulk material defects.
Semiconductors in general and solar cells in particular, feature negative electrons and positive “holes.” Because of material defects, these electron-hole pairs are often trapped and prevent the light transformation process from being efficient. The 3D cells these scientists experimented with, however, consist of n-type nanocones made of zinc oxide, surrounded by p-type semiconductor, made of polycrystalline cadmium telluride.
“We designed the three-dimensional structure to provide an intrinsic electric field distribution that promotes efficient charge transport and high efficiency in converting energy from sunlight into electricity,” Xu said.
Their approach improved the efficiency of existing planar solar cells made of the same materials from 1.8 to 3.2 percent, only by building nano-3D structures on the surface.
“The important concept behind our invention is that the nanocone shape generates a high electric field in the vicinity of the tip junction, effectively separating, injecting and collecting minority carriers, resulting in a higher efficiency than that of a conventional planar cell made with the same materials,” Xu also said.
3D solar cells are nothing new. Other researchers have studied some variations in the past, but, as far as I can recall, none had the remarkable outcomes Xu and his team managed to get.