Nov 7, 2012
CdTe coating improves photo-electron conversion efficiency of ZnO/CdS coaxial nanorods
Semiconductor nanocrystals exhibit an adjustable band gap, high stability and multiple exciton generation, while single crystalline nanowire arrays provide an ideal channel for effective carrier transport. To make use of these properties, developers assemble semiconductor nanocrystals on the surface of nanowires to construct so-called semiconductor sensitized solar cells. In a recent study, researchers have proposed to adopt sensitizers composed of both p- and n-type semiconductors to deliver structures that generate a built-in electrical field and promote charge separation as well as hole transfer.
To produce the combined structure, the team from Tianjin University, China, first fabricates n-type ZnO nanorod arrays on conductive glass substrates and then electrochemically deposits n-type CdS and p-type CdTe nanocrytals sequentially on the ZnO nanorods. The researchers found that the overall conversion efficiency of the ZnO/CdS/CdTe photoelectrode is more than three times the value of the sum of ZnO/CdS and ZnO/CdTe photoelectrodes.
Detailed investigations suggested that the cascade band structure of the ZnO/CdS/CdTe photoelectrode facilitated charge separation and hole transfer, which contributed to the improvement in overall conversion efficiency. A further enhancement in device performance can be anticipated by lengthening the ZnO nanorods and reducing the carrier recombination, such as adding an electron blocking layer outside the CdTe nanocrystals.
Full details can be found in the journal Nanotechnology.
About the author
Prof. Dr Xi-Wen Du, holds the Chair of “Functional Materials” and heads the Quantum Dots Materials and Devices group at Tianjin University, China. Dr Tao Ling graduated from Tsinghua University, China, and her research focuses on solar cells.