Fully solution-processed phase-pure 3D/2D perovskite bilayer heterojunctions

Combining the superior photovoltaic performance of three-dimensional perovskites and the intrinsic durability of two-dimensional perovskites, the construction of 3D/2D perovskite bilayer heterojunctions is a promising strategy to realize efficient and stable perovskite solar cells, but it is still a challenge to control the phase purity, film thickness, orientation, and crystal structure of 2D perovskites. Now, a solution-processing strategy has overcome this challenge by directly coating a tailored single-crystal 2D perovskite ink on as-prepared 3D perovskite films, resulting in effective, ultra-stable and phase-pure 3D/2D perovskite bilayer heterojunctions.