20.27% Efficient Carbon‐Based Hole‐Conductor‐Free Printable Mesoscopic Perovskite Solar Cells Achieved by Halogen‐free Room‐Temperature Post‐treatment

Abstract Defects at grain boundaries and energy level mismatch at the perovskite film/carbon electrode interface in printable mesoscopic perovskite solar cells (p‐MPSCs) lead to non‐radiative carrier recombination and large open‐circuit voltage ( V _OC ) losses. Herein, a method for post‐treating perovskite films in p‐MPSCs at room‐temperature using halogen‐free aromatic amines, including Benzylamine (BA), 1‐Naphthalenemethylamine (NMA), and 1‐Naphthalenecarboximidamide (NFA), is reported. The halogen‐free aromatic amines prevent the formation of iodine vacancy defects in perovskite films by interacting with under‐coordinated Pb ²⁺ , significantly reducing the trap state density of the perovskite films. Meanwhile, the halogen‐free aromatic amines can form low‐dimensional perovskites with type II energy level alignment at the perovskite film/carbon electrode interface, which significantly suppresses non‐radiative recombination of interfacial carriers and reduces V _OC loss. As a result, the champion power conversion efficiency (PCE) of p‐MPSCs based on NFA room‐temperature post‐treatment is improved from 17.51% in control devices to 20.27%, and the V _OC is increased from 0.975 V in control devices to 1.049 V. Furthermore, the unencapsulated p‐MPSCs retained more than 95% of their initial PCE after being stored in air for 3500 h. The halogen‐free room‐temperature post‐treatment provides a simple and green approach for preparing high‐efficiency and stable p‐MPSCs.