Studies of composite metal oxide-based ETA solar cells

The drive to produce low cost and efficient solar cells to replace solid state silicon cells has led to the rapid growth of nanotechnology in the PV sector. The extremely thin absorber (ETA) layer solar cell is a device that relies on the use of nanostructured anodes. The very high surface area of the metal oxides enhances the efficiency of the devices by increasing light harvesting in the cell. TiO2 has been the most common material of choice in these cells. However, alternative materials such as composite electrodes ZnO/TiO2, ZnO/SnO2, ZnO/Al2O3 have been considered. These systems also have the ability to improve charge carrier separation and broaden their photoresponse region. In addition to selecting materials with the correct energetics, the morphology of the metal oxide particles plays an important role in these devices. The ability to manipulate the shape, size, and surface to volume ratio of these oxides is critical in influencing the materials chemical, electronic and optical properties. In this thesis the fabrication of composite (ZnO,SnO2) electrodes by aerosol assisted chemical vapor deposition (AACVD) was investigated. By simply varying the Zn:Sn ratio in the precursor solution, a range of (ZnO,SnO2) composite materials along with single phase ZnO and SnO2 has been fabricated. It has been found that the morphology of the deposited electrodes is highly dependent on the Zn content with electrodes with morphologies ranging from nanoplates, to nanocolumns, to highly compact structures have been deposited. The dependence of the Zn content in the deposition solution on the photoelectrochemical (PEC), optoelectronic, photon to electron conversion efficiency (APCE) and photovoltaic characterization was investigated. ETA solar cells with FTO/(ZnO,SnO2)/In2S3/PbS/PEDOT:PSS/Cgraphite/FTO structures were successfully fabricated to demonstrate the suitability of (ZnO,SnO2) anodes in these devices. This work has shown that AACVD is a useful technique for engineering the properties of semiconducting electrodes for PV applications.