Engineering Spacer Conjugation for Efficient and Stable 2D/3D Perovskite Solar Cells and Modules.

Incorporating two-dimensional (2D) perovskite in 3D perovskite absorber holds great potential to improve the stability and efficiency of perovskite solar cells (PSCs). However, the bulky-cation-based 2D structures often exhibit poor charge transport and are prone to formation of charge-extraction barrier that impedes efficient device operation. We address these issues by introducing aromatic spacers with molecular conjugation into 2D perovskites locating between 3D perovskites and electron charge transport layers. Among our tested aromatic spacers, the pyrenylbutanamine (PyBA) spacer was shown to endow 2D perovskites with superior charge transport properties and efficient charge extraction from the bulk perovskite in 2D/3D PSCs, due to the highest degree of conjugation. As a result, we achieved a power conversion efficiency (PCE) of up to 25.3 % in a 0.16-cm single cell and 21.0 % in a 24.8-cm module. Moreover, the incorporated PyBA substantially raised the resistance of 2D/3D PSCs against moisture and ion migration, resulting in enhanced environmental, thermal, and operational stability. Notably, the PyBA-based devices retained over 90 % of their initial PCE after 2000 hours at 25 °C and 80 % relative humidity, or 1000 hours at 85 °C and 85 % humidity, or 3000 hours of operation under continuous 1-Sun illumination at 40 °C, showcasing their exceptionally high stability compared to previously reported 2D/3D PSCs.