Super-ion inspired colorful hybrid perovskite solar cells

Clean and sustainable energy is one of the greatest challenges of this century. Of the several renewable energy sources that can address this challenge, nothing has greater potential than solar energy. However, to harness the solar power and to ensure its world-wide uptake, efficient, cheap, environmentally benign, and durable solar cells are essential. The unprecedented enhancement in the power conversion efficiency of hybrid perovskite solar cells from 3.9% in 2009 to over 20% today shows their great promise to meet the above challenges, provided issues with their stability and environmental impact can be addressed. Despite considerable research in the past five years, answers to some fundamental questions as well as an atomic level understanding of these materials remain a challenge. Using multi-scale approach and a comprehensive study of over 40 materials, we have identified the key parameters and mechanisms that control the basic properties and the stability of hybrid perovskites. We show that these materials can be viewed as super alkali halide crystals where alkali and halogen ions are respectively replaced by super-alkali and super-halogen species. This opens the path to a new series of hybrid perovskites based on super-ions as building blocks with improved stability and functionality.