Deposition and characterization of thin films made with active layer from end life first generation solar cells

Photovoltaic technology is one of the most promising technology of the present and the near future. Nowadays several different solar cells are available in the market in order to try to meet the demand of different sectors which requires devices with different performance, thickness and flexibility to entirely cover the demand. However, the biggest part of the market share belongs to the crystalline silicon solar cells with over the 90% of the demand covered [1]. Furthermore, the demand of solar energy is estimated to grow another 60% in 2030, reaching 31600 TWh [1]. With these premises, it is evident that silicon solar panels are massively impacting the environment in a way that is not always positive: although it is true that renewable energy sources such as the solar one currently seems the best solution to keep our energy needs away from fossil fuels, there are still negative evidences concerning researchers all over the world, especially because of the massive pollution generated during the production of the silicon and the assembly of the photovoltaic module. During the production of silicon modules, in fact, a lot of chemicals are used in order to purify, deposit, build contacts, and all the other necessary steps to produce the final result. Another major concern regards the disposal of the photovoltaic modules after their lifetime: it can be assumed that the lifetime of a solar panel varies from 15 to 30 years according to the initial year of installation, which underlines the technological improvements made year by year in the solar sector [2]. After this amount of time, the easiest way to dispose of solar modules is the landfilling, which is also the most negatively impacting from an environmental point of view. In order to avoid it and find the most useful way to give a new birth to the various materials used in the photovoltaic technology, many recycling processes were ideated, with the active layer of silicon as the heart of these processes. Usually the followed path is the leaching: through the use of chemicals the active layer is purified from all the contacts and materials that were needed during the working time of the PV. Although it is an easy way to recycle silicon, it is still not environmentally friendly under all aspects: the use of chemicals such as toxic gases and strong acids it is always associated with some damage. In this work will be discussed the possibility to generate new value for crystalline solar cells trying to exploit the semiconductor active layer just with thermochemical processes. Not just recycle into new solar cells will be discussed, but also the possibility to exploit the new silicon for other applications such as sensors or optical devices. The characterization will be conducted on thin films of the recycled material after depositions through thermal evaporation, and several experimental setups will be used for its characterization, such as Hall effect measurement, Jaasco spectrophotometer, Seebeck coefficient measurement, I-V curves experimental setup and V-t curves experimental setup in order to explore the potential of the deposited materials with and without further treatments and of simple p-n junctions built with a monolayer of the same material, recycled active layer from first generation solar cells waste.