A favored crystal orientation for efficient printable mesoscopic perovskite solar cells†
Controlling the crystal orientation of organic–inorganic hybrid perovskites is crucial in tuning the optoelectronic properties and improving the device performance. Herein, the favored crystal orientation of MAPbI3 perovskite is finely tuned by additive engineering for carbon based printable mesoscopic perovskite solar cells (PSCs). By introducing biguanide hydrochloride (BH), the out-of-plane crystal orientation of perovskite film is notably enhanced along the (001) and (002) crystal plane, which affects charge transportation and collection properties of perovskite films. More importantly, the BH added perovskite has the most appropriate energy level. Under the optimized condition, the hole-conductor free printable mesoscopic PSCs deliver a champion power conversion efficiency of 16.35% by introducing a 30% molar ratio of BH. The unsealed device retains 98% of its original PCE after 2500 h storage in air with humidity of 50 ± 5%. The results provide a novel and effective approach toward fabricating highly efficient and stable PSCs for future commercialization.