Powered by the Sun – at a fraction of the cost
Harnessing the energy of the Sun to produce electricity is about as sustainable as one might hope to get. The Sun’s energy is virtually limitless and, if production processes are favourable, electricity production is low- to no-emission. The catch to a certain extent is the cost and efficiency and perhaps the trade-off between the two. While the presence of photovoltaic (PV) devices on the market has increased dramatically, large-scale household systems are still not commercially viable. The key to solar energy deployment on a large scale will be new technologies for higher energy conversion efficiency and lower production costs. Most PV devices in use are based on single- or multi-crystal silicon (Si). Emerging technologies are based on thin films, materials created by the growth of various species on a substrate. European scientists sought to develop materials and processes for high-throughput, cost-effective production of thin-film solar cells. With EU funding of the 'Thin Si film based hybrid solar cells on low-cost substrates' (Thinsi) project, scientists are developing solar cells with structures similar to those of conventional bulk crystalline Si wafers but using a low-cost Si substrate to substitute the Si wafer. The substrate will be made from inexpensive materials using state-of-the-art ceramics technologies (powder-to-substrate concept yielding wafer-equivalent technology) and inexpensive processes developed by the project consortium. Initial work focused on obtaining Si powder of desired purity, crystalline structure and particle size for use in the spark plasma sintering (SPS) method. Optimisation of the SPS process resulted in fabrication of dense and highly conductive Si substrates. Scientists have also conducted extensive investigations regarding Si layer deposition on the substrates. The properties of such layers are currently being studied. Reference solar cells on both crystalline and thin-film substrates have been fabricated and efficiencies evaluated and compared. Finally, a cost model for a Thinsi solar cell has been developed based on estimated solar energy conversion efficiency. Thinsi expects to deliver low-cost, high-throughput materials and fabrication technology for thin-film solar cells that may overcome the current cost barrier preventing widespread deployment of solar energy systems.
