Optimizing the fabrication process for next generation nano-textured solar cells with high conversion efficiency using industrially viable solar cell processes

The need for photovoltaic (PV) cells with high conversion efficiency and low surface reflectance has been on the rise. With this in mind, the fabrication process of PV cells has been investigated with interest in the surface etching phase in order to reduce surface reflectance using nanotexturing. The purpose of this thesis is to investigate how to improve the etching phase by optimising the key parameters for an atmospheric dry etch (ADE) with different processes to determine which can aid in reducing surface reflectance. To obtain a process which provides a low surface reflectance, parameters in the etching phase are changed, including multicrystalline versus monocrystalline , the etch time and the use of different cleaning techniques. Once the Si wafers have been put through the etching process, they are tested using a spectrometer to determine surface reflectance. A scanning electron microscope (SEM) and an atomic force microscope (AFM) were then used in order to observe how the etching process has affected the surface morphology. Different parameters have been shown to have a varying effect on the surface reflectance of the etched Si surface, in particular cleaning processes before etching and etch time. Etch time has shown to have the greatest effect on surface reflectance. It can be seen that reflectance will vary with etch time as a result of the chemical reaction between the Si found on the surface of the Si wafer and the etching gas. Certain conditions influence the Si etch rate and surface reflectance better than others. Further investigation into the use of multicrystalline silicon (mc-Si) using monocrystalline Si samples as a reference to assist in determining optimum etching phase. Etched mc-si samples can be processed using the same parameters and cleaning processes as the monocrystalline Si, resulting in identifiable crystal orientations. Application of the same test conditions in order to determine the surface reflectance and morphology will provide a further insight to what degree the etching phase needs to be improved upon in order to obtain low surface reflectance