Hybrid perovskites for photovoltaics: Story, challenges and opportunities

Organic-inorganic hybrid perovskites have been representing a scientific breakthrough in the photovoltaic field since 2009 when they were applied to replace photoactive dyes in hybrid solar cells. Further development has been highly boosted by a large and enthusiastic effort up to a current maximum efficiency of 24.2%. The exceptionality of this class of materials resides in their soft character combined with long diffusion lengths of the photo-generated carriers, a wide absorption range and direct tunable bandgap. Nonetheless, the low structural stability of the hybrid perovskites, primary MAPbI3, risks to severely retard their wide-range applications in low-cost/high-yield devices. Focused research is currently relating instability sources and degradation mechanisms with the operation conditions, including temperature, illumination, humidity, contaminants and interfacing materials. Although the overall scenario is brighter than years ago, reliable and long-lasting solutions to avoid back-reaction of perovskites to the starting byproducts and indeed to extend cell durability are under spotlight. For the market uptake, moreover, device architectures to be produced via simple and sequential steps, free of contaminants and at low environmental impact, are warmly encouraged to catch the interest of investors. The paper will thus frame strengths and weaknesses of hybrid perovskites for next-generation photovoltaics in view of their extended use and dissemination in daily life.