Review of Recent Progress of Lead-Free Perovskite Materials for Photovoltaic Applications

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Lead-free perovskites have been identified as potential materials for replacing the typical lead-based perovskites for photovoltaic (PV) applications due to the major drawback related to their toxicity that negatively influences environmental sustainability. This review provides a general research overview of the recent advances for lead-free perovskites for PV device applications, including perovskites based on tin, germanium, bismuth, antimony, and double junction materials. The review presents recent advancements achieved from both experimental and density functional theory (DFT) investigations, and discusses the progress in examining the structural, electronic, optical, and defect characteristics of these perovskites. Special focus is given to bandgap engineering, defect effects, and charge transport properties. Furthermore, recent achievements reported for device structures and fabrication techniques, including spin, blade, and slot-die coating along with vapor deposition, are reviewed in detail. While lead-free perovskite PVs reveal high potential for applications, their efficiency is still less than that of lead-based ones due to restrictions related to their stability, defect density, and charge transport characteristics. Lastly, the possible research directions for additional research in this field are discussed.