3,5-dichlorobenzylamine lead high-performance and stable 2D/3D perovskite solar cells

Organic-inorganic lead halide peroxides (OIHPs) have attracted much interest due to their excellent photovoltaic properties, but practical applications are limited by long-term stability and further performance enhancement. Two-dimensional/three-dimensional (2D/3D) heterojunction is a promising strategy to address these issues. Here, short-chain 3,5-dichlorobenzylamine (DBA) with halogen functional groups is introduced to react with excess PbI2 to form the 2D perovskite layer in mixed perovskite films of Cs-0.05(FA(0.85)MA(0.15))(0.95)Pb(I0.85Br0.15)(3), which passivates surface defects, favours energy band alignment of functional layers and suppresses non-radiative recombination of carriers. As a result, DBA-treated 2D/3D PSCs obtained a champion PCE of 21.54% with an improved open circuit voltage (V-oc) of 1.171 V. More importantly, the 2D/3D heterojunction can effectively protect the underlying 3D perovskite from moisture ingress. The unencapsulated 2D/3D devices retain 90% of their initial efficiency even after aging at 40 +/- 5% RH for 1000 h, while the 3D device retains only 40%.