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

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) 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, 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 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 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.