Europe has set the energy transition to renewable sources as a priority policy to minimize the effects of climate change. Photovoltaic (PV) energy is called to play a major role in the world’s electricity production in the mid-term. The present market-dominant technology, crystalline silicon (Si), has reached its practical efficiency record of 26%, and the energy cost of this technology – which has been diminishing in the last decades, following a technology learning curve – seems to be stagnating now. Given the in-creasing fraction of the total cost of PV electricity represented by area-related costs (e.g. encapsulation and field-installation), any improvement in the solar cell’s efficiency will partly translate in a further reduction of the PV electricity price. For this reason, research on new ways of increasing the conversion efficiency of solar cells is still extensive. In parallel, PV is expected to expand in distributed autonomous systems, with thin solar cells supported on a variety of rigid or flexible (e.g. polymers and metal foils) low-cost substrates; thereby fostering a wide range of solar-powered systems for portable electronics, electric cars, medical diagnostic, smart-packaging, etc.
Among the proposed novel concepts for high-efficiency solar cells, the intermediate band solar cell (IBSC) has received great attention by the scientific community. In conventional single-gap solar cells, photons with energy lower than the bandgap of the absorber material are wasted. The IBSC concept allows harvesting below-bandgap photons without voltage loss, which increases the limiting efficiency from 33% to 50%. So far, IBSCs have been realized with epitaxially-grown quantum-dot (QD) super-lattices of III-V semiconductors. However, no pronounced efficiency enhancement has been yet report-ed, since this technological approach is unable to produce nanostructured materials with the required opto-electronic properties. Recently, a new family of semiconductor materials, colloidal QDs in a perovskite host (CQDs@Perovskite), has emerged as a promising way to develop efficient IBSCs. This project’s goal is to exploit CQDs@Perovskite materials combined with microstructure-based light trap-ping to pave the way for low-cost high-efficiency solar cells, compatible with flexible- substrate technology.
