Modern concepts enabling very high efficiencies beyond the single junction Si solar cell limit with low-cost fabrication are required to make PV technology competitive with conventional energy sources. Tandem solar cells are a promising route to enhance solar cell efficiencies. The lack of a suitable low-cost high-efficiency top cell has inhibited the fabrication of c-Si based tandem devices. However, with the emergence of perovskite solar cells (PSCs), the tandem cell concept has received a major boost. Theoretical studies have predicted efficiencies far in excess of 30% for c-Si based tandem cells with PSC as the top cell. Experimental work on this tandem concept has been started by a few research groups in Australia, Europe and USA in the past 2 years.

The Si-perovskite tandem architecture is a promising and important concept, considering the potentially ultra-high efficiencies that are possible with this design. In India, Si solar cells with efficiencies of 15-17% are available commercially. If the tandem architecture is able to boost these efficiencies beyond 20%, without significant increase in production costs, it will be a great achievement and lower the cost of electricity from solar PV modules. The perovskite cells can be solution processed on top of Si cells and therefore, offer a low-cost opportunity to increase the solar cell efficiencies. The present research proposal is, therefore, important in many aspects. It aims to start the research work on tandem designs in India and promises to deliver realistic efficiencies >20% for solar cells fabricated by an already established industrial base in India.