Constructing 2D passivation layer on perovskites based on 3-chlorobenzylamine enables efficient and stable perovskite solar cells

The carbon-based hole transport layer-free (HTL-free) PSCs show promising potential for commercialization stemming from the economy and chemical inertia of carbon electrodes. While the huge energy barrier between the perovskite layer and carbon electrode results in severe energy loss and poor stability simultaneously. Herein, 2D perovskite as a passivation layer is successfully constructed with the help of 3-chlorobenzylamine (3Cl-BA), which is anchored on the surface of methylamine lead iodine (MAPbI3) perovskites by forming NH–I hydrogen, forming Cl–I bond and filling the halide vacancies, thereby suppressing the energy loss and protecting perovskites from moisture ingress. Detailed experimental characterizations prove that the 3Cl-BA passivation layer could optimize energy level and prolong the carrier lifetime of the perovskites. As a result, a gratifying power conversion efficiency (PCE) of 13.22 % is obtained for carbon-based HTM-free PSCs based on the 3Cl-BA treated MAPbI3 perovskite by optimizing the post-treatment conditions. What's more, owing to the existence of the hydrophobic 2D structure, the unencapsulated PSC exhibits better long-term moisture stability. It remains at 95 % of the original PCE after aged under the environment of the nitrogen for 800 h. This post-treatment based on 3Cl-BA provides a bright road to preparing efficient and stable PSCs via forming 2D/3D perovskite structures.