Current Advancements in Material Research and Techniques Focusing on Lead-free Perovskite Solar Cells

Organic-inorganic lead halide perovskite solar cells (PSCs) recently achieved a photo-to-electricity conversion efficiency (PCE) of 22.1%. They drew much attention as promising photovoltaic devices. However, the Pb-based PSCs face great challenges for commercial and industrial applications due to the instability and the toxicity of perovskite materials. Herein, we summarize the current development of various types of Pb-free perovskites, such as the Sn-, Bi-, Ge-, Sr-, and Cu-based perovskites and their devices. In addition, we will address some remaining issues and prospects of the Pb-free PSCs