The Effect of Embedded Ag versus Au Nanoparticles on the Photovoltaic Conversion Efficiency in CdTe/CdS Thin Films*

The addition of metal nanoparticles to photovoltaic cells creates the possibility of improving cell efficiency and reducing production costs. Impressive improvements in photovoltaic conversion efficiencies were found in CdTe/CdS/ITO (indium tin oxide) based solar cells with the addition of embedded Ag nanoparticles. Ag nanoparticles were deposited between the CdS and CdTe layers through pulse laser deposition method. Structural and electrical characterizing was achieved using x-ray diffraction ellipsometry, scanning electron microscopy, energy dispersive x-ray diffraction, atomic force microscopy and Keithley source meter photovoltaic measurement set. Previous research revealed that the photovoltaic conversion efficiency exhibits sensitive dependence on the size and the particle density of the embedded Ag nanoparticles. This work focuses on identifying at what amount of Ag deposition time will yield maximum efficiency. A similar study was conducted using Au nanoparticles deposited with the same parameters. An assessment of the differences between Ag and Au nanoparticles size and density was done. More importantly, a comparison on the photovoltaic conversion efficiency in thin films with Au versus Ag nanoparticles will be discussed.