Spacer Engineering of Thiophene-Based Two-Dimensional/Three-Dimensional Hybrid Perovskites for Stable and Efficient Solar Cells

Organic spacers play a crucial role in two-/three-dimensional (2D/3D) hybrid perovskite-based solar cells that integrate the advantages of the stability of 2D perovskites and the high efficiency of 3D perovskites. However, improving the stability of the device without compromising the high photovoltaic efficiency in 2D/3D perovskite solar cells using large organic cations in 2D perovskite is a challenge. Herein, we synthesized 2-thiopheneethylammonium iodide (TEAI) and found that TEAI can perform as a spacer for 2D/3D hybrid perovskites. TEAI with a bulky aromatic spacer in 2D/3D hybrid perovskites can effectively induce crystalline growth and orientation, leading to a longer carrier lifetime, higher carrier mobility, fewer surface, and grain boundary defects. The inclusion of TEAI also improves surface hydrophobicity. The 2D/3D hybrid perovskite device based on TEAI achieved the highest efficiency of 18.75% compared with the 16.83% efficiency of the 3D perovskite device. After aging for 1000 h in an ambient atmosphere, the unpackaged 2D/3D hybrid perovskite solar cells maintained approximately 82% of their initial efficiency, whereas that of the controlled devices decreased to approximately 47% of their original performance. These results suggest that TEAI can be used as an organic spacer for the preparation of high-efficiency and high-stability 2D/3D perovskite solar cells.