Coupling Alkali Metal and Organic Cations to Form Oriented Quasi-2D Perovskite for High-performance Solar Cells

Two-dimensional (2D) perovskite solar cells that boast of high stability and high efficiency have attracted significant attention. A systematically static and dynamic structure investigation is carried out to show the details of 2D morphology evolution. A dual additive approach is applied, in which the synergic efforts of alkali metal cation and polar solvent lead to high quality 2D perovskite thin film with well orientation. The novel structure can induce high quality 2D slab growth as well as reduce internal and surface defects, thus resulting in a high device efficiency of 13.65%. Steady-state and transient absorption spectra reveal the carrier transporting from low n to high n species of different kinetics. An [PbI₆]^4- octagon coalescence transformation mechanism coupled with metal and organic cations wrapped is proposed, which then subjects to solvent vapor annealing to recrystallize and reorient 2D perovskite slabs to form an ideal structure to give rise to the improvement of device efficiency and stability.