Tailoring Low-Dimensional Phases for Improved Performance of 2D–3D Tin Perovskite Solar Cells

2D–3D tin perovskites are considered as promising candidates for realizing efficient lead-free perovskite solar cells (PSCs). However, the ultrathin 2D phases could unfavorably affect charge transport and device performance. In the present work, we demonstrate that the introduction of D-homoserine lactone hydrochloride (D-HLH) can tailor the low-dimensional phases and improve the quality of 2D–3D tin perovskite films. The functional group in D-HLH can interact with FA⁺ and I^– as well as Sn²⁺ in the precursor solution. These interactions not only affect the formation of tin perovskite film and favor the formation of thicker 2D phases but also decrease the defect density and suppress the nonradiative recombination. As a result, the efficiency of tin PSCs is significantly improved from 7.97 to 12.45%, and the stability of the device is also enhanced. This work provides a feasible strategy to regulate the low-dimensional phases in 2D–3D tin PSCs toward realizing high efficiency.