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

Abstract

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 NiO_x, 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.