Device Proves Solar Cell Potential Of High Bandgap İnorganic Nanowire Arrays

A report, published in the March 14 edition of the Journal of Materials Chemistry, announced the successful fabrication and testing of a new type solar cell using an inorganic core/shell nanowire structure. Arrays of core/shell nanowires (described has "quantum coaxial cables") had previously been theorized as a potential structure that, while composed of chemically more stable large bandgap inorganic materials, should also be capable of absorbing the broad range of the wavelengths present in sunlight. High bandgap semiconductors are generally considered not effective at absorbing most of the available wavelengths in solar radiation by themselves. For instance, high bandgap zinc oxide (ZnO) is transparent in the visible but absorptive in the ultraviolet range, and thus is widely used in sunscreens but was not considered useful in solar cells.

In the report, a team of researchers from Xiamen University in China and the University of North Carolina at Charlotte describe successfully creating zinc oxide (ZnO) nanowires with a zinc selenide (ZnSe) coating to form a material structure known as a type-II heterojunction that has a significantly lower bandgap than either of the original materials. The team reported that arrays of the structured nanowires were subsequently able to absorb light from the visible and near-infrared wavelengths, and show the potential use of wide bandgap materials for a new kind of affordable and durable solar cell.

"High bandgap materials tend to be chemically more stable than the lower bandgap semiconductors that we currently have," noted team member Yong Zhang, a Bissell Distinguished Professor in the Department of Electrical and Computer Engineering and in the Energy Production and Infrastructure Center (EPIC) at the University of North Carolina at Charlotte.

"And these nanowire structures can be made using a very low cost technology, using a chemical vapor deposition (CVD) technique to grow the array," he added. "In comparison, solar cells using silicon and gallium arsenide require more expensive production techniques."

Based on a concept published in Nano Letters in 2007 by Zhang and collaborators Lin-Wang Wang (Lawrence Berkeley National Laboratory) and Angelo Mascarenhas (National Renewable Energy Laboratory), the array was fabricated by Zhang's current collaborators Zhiming Wu, Jinjian Zheng, Xiangan Lin, Xiaohang Chen, Binwang Huang, Huiqiong Wang, Kai Huang, Shuping Li and Junyong Kang at the Fujian Key Laboratory of Semiconductor Materials and Applications in the Department of Physics at Xiamen University, China.