Regulating the lattice strain in perovskite films to obtain efficient and stable perovskite solar cells

Lattice tensile strain generated during the preparation of perovskite thin films has detrimental effects on the efficiency and stability of perovskite solar cells (PSCs). Herein, an additive with a conjugated structure, 2,2′-diamino-[1,1′-biphenyl]-4,4′-dicarboxylic acid (DBDA), containing amino and carboxyl groups was introduced to convert tensile strain to compressive strain in perovskite films. The amino and carboxyl groups of DBDA interacted with the main components of perovskite precursors (PbI2 and FAI). These interactions slowed perovskite crystallization, enabling the formation of large grains, passivating defects in perovskite films, transform tensile strain of perovskite films into compressive strain and thus improving the performance and stability of the resulting PSCs. The champion power conversion efficiency of the DBDA-treated PSCs increased to 24.57 %, and 19.66 % for the module with an active area of 14 cm2. Furthermore, the DBDA-treated PSCs remained 92 % of its initial efficiency after 1000 h of continuous illumination. This work provides a new method for regulating lattice strain to prepare efficient and stable PSCs.