Vertically Oriented Calixarene Self-Assembled Monolayers Enable Efficient Tin-Based Perovskite Solar Cells.

Self-assembled monolayers (SAMs) represent an effective strategy for optimizing buried interfacial quality in tin-based perovskite solar cells (TPSCs). Nevertheless, conventional SAMs often suffer from severe molecular agglomeration, deteriorating interface quality, and tend to adopt a "lying-down" configuration on hole transport layers, leading to a reduced vertical dipole component and limited ability to tune mismatched energy level alignment. Herein, a multifunctional SAM, 4-sulfocalix[6]arene (SC6A), is introduced to simultaneously regulate the buried interface and optimize band alignment in TPSCs. Owing to six anchoring sulfonate groups, SC6A forms robust multidentate interactions with NiOx, enabling homogeneous interfacial coverage and improved perovskite film growth. Meanwhile, SC6A possesses a large intrinsic molecular dipole and preferentially adopts a vertical orientation, which maximizes the effective dipole component normal to the interface, induces favorable band alignment, and accelerates charge extraction. As a result, TPSCs with SC6A exhibit a power conversion efficiency (PCE) of 16.46%. TPSCs with SC6A maintain 98% of their initial PCE after 980 h of shelf storage. Furthermore, the TPSC with SC6A maintains 90% of its initial PCE after 300 h of continuous operation under 1-sun illumination, whereas the control device reaches the same retention level after only 146 h, demonstrating enhanced long-term operational stability.