Si/ZnO nanorods with Ag nanoparticles/AZO heterostructures in PV applications

Our studies focus on test structures for photovoltaic applications based on zinc oxide nanorods grown using a low-temperature hydrothermal method on a p-type silicon substrate. The nanorods were covered with silver nanoparticles of two diameters – 20–30 nm and 50–60 nm – using a sputtering method. Scanning electron microscopy (SEM) micrographs showed that the deposited nanoparticles had the same diameters. The densities of the nanorods were obtained by means of atomic force microscope (AFM) images. SEM images and Raman spectroscopy confirmed the hexagonal wurtzite structure of the nanorods. Photoluminescence measurements proved the good quality of the samples. Afterwards an atomic layer deposition (ALD) method was used to grow ZnO:Al (AZO) layer on top of the nanorods as a transparent electrode and ohmic Au contacts were deposited onto the silicon substrate. For the solar cells prepared in that manner the current-voltage (I-V) characteristics before and after the illumination were measured and their basic performance parameters were determined. It was found that the spectral characteristics of a quantum efficiency exhibit an increase for short wavelengths and this behavior has been linked with the plasmonic effect.