Although the sun is the cheapest source of energy on the Earth, the conversion of its light into electricity is still one of the most expensive. The application of photovoltaic (PV) cells/modules to convert sun light is one of several ways to lower fossil energy consumption, decrease CO2 emission and diversify energy sources. Unfortunately, the PV module production costs still limit utilization of this energy source in common daily use. Therefore, we propose a solution that can lead to simplification of the PV cell fabrication resulting in final decrease of their costs and thus, to lowering the financial barrier for all. Nowadays, the n+/p and p/p+ junctions formation, which is the basic Si solar cell part, is performed in separate processing steps. In this project we are going to modify the junction formation methodology that can be applied in-line. Moreover, the n+/p junction formation with the use of liquids instead of gaseous and toxic PClO3 allows construction of simple and cheaper production systems. The p/p+ junction can be also formed from liquid or steady sources replacing conventional paste application. Such approach should significantly simplify PV cell production due to shortening of the processing time and lower costs of technological procedures. Additionally, combining the fast texturization by catalytic nanoparticles application with the plasmonic nanoparticle systems deposited on the cell surface should increase the cell efficiency. The PV cells and modules of higher efficiencies, which can be produced at lower fabrication costs than the present ones, will be the main outcome of the proposed project.
The set of the bifacial silicon solar modules fabricated with the use of developed technology. The view from p+ emitter.
The costs of photovoltaic (PV) module fabrication limit utilization of this energy source in common daily use. The n+/p and p/p+ junctions must be formed at semiconducting silicon surface by surface doping with phosphorus or boron. This doping process of silicon wafers is commercially implemented in separate steps that create additional costs. The costs can be lowered by when in-line process of junctions’ formation is applied. The InlinePV project was focused on developing simpler, environmentally benign and cheaper methods for silicon doping to form necessary junctions. This task was achieved for phosphorus or boron dopants applied on silicon wafers. The developed method utilized liquid sources of the dopants. The dopant solutions were composed of simple inorganic (phosphoric or boric acids) and organic compounds (alcohols). The applied compounds were neither toxic nor expensive contrary to the ones used in commercial processes. The sources were deposited at silicon surface by simple and cheap spray method allowing in-line application. The depth profiles of dopant distribution were adequate to the PV cell requirements. The phosphosilicate and borosilicate glasses formed at the silicon surface during high temperature doping process were much easier removable than the ones formed after commercial POCl3 or BBr3 dopants were used. The efficiencies of the cells fabricated with the use of developed sources were the same like obtained with application of POCl3 or BBr3 commercially used. Therefore, by application of developed doping system we were able to lower costs of environmental protection during the fabrication process, costs of chemical compounds used for doping process and costs of fabrication based on in-line technology. Additionally, the studies on application of metal assisted etching for silicon surface texturization led to selection a bimetallic system containing Ag and Pd that resulted in lower surface reflectance than the single metals used. The noble metals deposition by magnetron sputtering allowed in-line method utilization. The acidic etching resulted in removal of metallic contaminations from the etched surface that made the method industrially applicable. The works on application of plasmonic particles and light converters at the front surface of the solar cells were performed. The results were scientifically interesting but light conversion effect was too low to be commercially applicable. The cells and modules fabricated with developed technology were thoroughly characterized. The opto-electrical parameters and physicochemical properties of the construction details were determined. As a proof of the developed technology five PV modules were fabricated. In summary, the developed technological solutions offer lowering of the costs of PV cells/modules fabrication with the same efficiency like obtained by application of commercial technology that can finally led to broader availability of environmentally benign technology of electricity production.