Band Alignment Boosts over 17% Efficiency Quasi-2D Perovskite Solar Cells via Bottom-Side Phase Manipulation

Quasi-2D perovskites have attracted extensive attention due to their extraordinary stability compared to their 3D counterparts. Presently, the bottleneck in quasi-2D perovskite solar cells is their relatively low efficiency. The intrinsic interior carrier transport in the perovskite layer consisting of disorderly oriented phases and inadequate optimization of interfacial carrier transfer have greatly limited the overall device performance. A comprehensive study on effective phase manipulation in the BA₂MA₄Pb₅I₁₆ (n = 5) quasi-2D perovskites is presented to pursue optimal efficiency. With the assistance of the solvent DMSO in a constant thermal-annealing spin-coating (CTAS) process, the crystalline growth process in the quasi-2D perovskite film is effectively manipulated and delicate energy band alignment by eliminating the n ≤ 2 phases at the bottom surface has been successfully achieved. Consequently, a significant improvement of carrier transport in the perovskite layer and photogenerated hole extraction at the interface has been accomplished. The champion device exhibited a boosted PCE of 17.66%.