Ligand‐Induced In Situ Epitaxial Growth of PbI2 Nanosheets/MAPbI3 Heterojunction Realizes High‐Performance HTM‐Free Carbon‐Based MAPbI3 Solar Cells

Hole-transporting layer-free carbon-based perovskite solar cells (HTL-free C-PSCs) hold great promise for photovoltaic applications due to their low cost and outstanding stability. However, the low power conversion efficiency (PCE) of HTL-free C-PSCs mainly results from grain boundaries (GBs). Here, epitaxial growth is proposed to rationally design a hybrid nanostructure of PbI