Self‐assembling Monolayer‐Assisted Perovskite Growth Enables High‐Performance Solar Cells

Comprehensive Summary Inverted (p‐i‐n) perovskite solar cells (PSCs) are favored by researchers owing to their superior compatibility with flexible substrates and tandem device fabrication. Additionally, the hole transport layer (HTL) serves as a template for perovskite growth, which is critical for enhancing the device performance. However, the current research on how the HTL promotes perovskite crystallization is insufficient. Here, 4PADCB, a self‐assembled monolayer (SAM) hole transport material, was optimized as a superior template for perovskite growth through comparative analysis; accordingly, compact perovskite film with vertical growth was prepared. The better matched energy level alignment between 4PADCB and perovskite suppressed nonradiative recombination at the interface and enabled rapid hole extraction. Moreover, high‐quality perovskite film growth on 4PADCB exhibited lower Young's modulus and less residual stress. By integrating 4PADCB into p‐i‐n PSCs, the optimal device achieved a power conversion efficiency of 24.80%, with an open‐circuit voltage of 1.156 V, thus achieving the best rank among devices without perovskite post‐treatment, additives, dopants, or intermediate layers. Furthermore, the unencapsulated device demonstrated exceptional thermostability and photostability under maximum power point tracking. Thus, this work provides a new understanding for the development of novel SAMs and perovskite growth, and it is expected to further improve device performance.