Enhancing the Stability and Performance of Two-Dimensional Perovskite Solar Cells via Double-Step Homogeneous Precursor Mixing

Two-dimensional (2D) perovskites have received significant attention as eminent solar cell absorbers mainly due to their structural tunability and high stability compared to their three-dimensional (3D) counterparts. These materials have been mostly prepared using a solution process; thus, their optoelectronic properties and intrinsic stability depend critically on the characteristics of the precursor solutions. Here, for the first time, a double-step homogeneous precursor mixing process is employed to enhance the quality and stability of 2D perovskite precursor solutions and the corresponding solar cells. To attain the precursor solutions via such a process, a solution comprising PbI2 and a bulky spacer such as propane-1,3-diammonium iodide (PDAI2) was first made followed by the addition of a methylammonium iodide (MAI) solution. This facile double-step process enabled the formation of particularly stable solvation complexes as a result of the significantly enhanced interactions between the solvent and precursors. Hence, the obtained precursor solutions had high uniformity and stability. Additionally, the prepared 2D (PDA)(MA)n-1PbnI3n+1 (n = 5, 10, and 15) films exhibited several remarkable properties, including an exceptionally smooth surface with enhanced crystallinity, highly stable crystal structures, and excellent moisture resistance, compared to the films prepared via the conventional precursor mixing process. Consequently, unsealed solar cells based on these 2D perovskite absorbers delivered power conversion efficiencies (PCEs) of up to 6.35% at n = 15 with high stability in humid air (relative humidity exceeding 70%), whereas the devices fabricated via the conventional process demonstrated considerably lower PCEs and stability. These results revealed that this newly developed process opens up new avenues in the fabrication of highly stable and efficient 2D perovskite solar cells.

Automated summary

A double-step homogeneous precursor mixing process was used to enhance the quality and stability of 2D perovskite precursor solutions, leading to highly stable and efficient solar cells.