FundamentaLs and Application of Silicon Heterojunction solar cells (FLASH)

Although the price of solar panels has recently decreased considerably, the production cost of solar cells is still too high for the generated electricity to compete with bulk electricity prices. The STW Perspectief programme FLASH aims at reducing the production costs of photovoltaic (PV) modules considerably, so that PV systems can be deployed widely and provide a large fraction of sustainable electricity. This is achieved by improving the solar cell conversion efficiency, reducing materials consumption and using abundant materials only, and by applying low-cost and low-temperature processing methods, which lowers the energy costs in manufacturing as well. We focus on silicon heterojunction (SHJ) solar cells, because they combine the high efficiency of crystalline silicon (c-Si) wafer technology with the high throughput, low-cost production technologies for amorphous silicon thin-film solar cells. Thin film technology provides excellent methods for surface passivation and junction formation at low processing temperatures. Surface passivation, a method to electronically de-activate defects at the interface, is crucial for reducing losses in SHJ solar cells and leads to very high efficiencies. Through novel cell design the efficiency is potentially even higher than wafer-based technologies using conventional diffusion processes for junction formation.

SHJ technology, as an alternative to conventional c-Si wafer-based PV technology, will result in lower mechanical stress, which facilitates the use of thinner wafer material. This facilitates a major contribution to cost reduction and improves the environmental profile of solar electricity significantly. The fundamental knowledge that is necessary for a breakthrough in costs and cell efficiency is provided by the FLASH Perspectief programme, primarily by (i) smart defect engineering, and (ii) the development of new silicon heterojunction cell structures and their production technology. A new structure to be developed is a fully back-contacted cell that has both positive and negative contacts at the rear of the device. FLASH will demonstrate a high conversion efficiency (>21%) for novel SHJ cell designs and technologies at low cost that can be applied to thin wafers (< 100 µm). FLASH will also provide the fundamental knowledge on new process technologies and design that will lead to 25% solar cell efficiency using even thinner wafers (~50 µm).