Scientists from Various Universities (1. Mössbauer Effect Data Center, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China, 2. Centre for Solar Energy Materials, International Advanced Research Centre for Powder Metallurgy and New Materials, Hyderabad 500005, India, 3. Department of Materials Science and Engineering, City University of Hong Kong, Kowloon Tong, Hong Kong SAR, 4. Tokyo University of Science, Kagulazaka 1-3, Shinjuku, Tokyo 162-0825, Japan)  and their research collaboration team have discovered hierarchical Sn and AgCl co-doped TiO 2 microspheres as an electron transport layer for the enhanced perovskite solar cell performance.   Zero carbon emission by low-cost and environmentally-friendly alternative energy resources is required for the growing world’s energy demand. Concerning this, perovskite solar cells (PSCs) have gained more attention in recent years, owing to their low cost, higher absorption coefficient, and high ef...