Molecular Tailoring of Self-Assembled Monolayers Derived From Asymmetric Benzothienoindole for Efficient and Stable...

Self-assembled monolayers (SAMs) have emerged as efficient hole-transporting materials for inverted perovskite solar cells (PSCs). However, the synergistic design of SAMs that simultaneously optimizes electronic structure, molecular packing, perovskite crystallization, and interfacial contact remains underexplored, and the development of new SAMs is often impeded by complex synthetic routes. Herein, we developed an asymmetric [1]benzothieno[3,2-b]indole (BTI) core via a concise Fischer indole synthesis. From this core, three SAMs are obtained by sequentially introducing substituents with electron-donating to electron-withdrawing characteristics. As the electron-withdrawing ability of the substituents increases, the SAMs exhibited progressively enhanced electron delocalization, improved energy-level alignment with perovskite, and preserved long-range ordered molecular packing. The improved SAMs film quality enables them to act as effective templating layers for perovskite deposition, directing perovskite crystallization, improving buried interfacial contact, and suppressing interfacial nonradiative recombination. Consequently, the inverted PSCs with F-4PABTI deliver a champion power conversion efficiency (PCE) of 26.76%, a high open-circuit voltage (V_OC) of 1.203 V, and markedly improved operational stability. Notably, the large area device (1 cm²), module (655.2 cm²), and wide-bandgap device (1.84 eV) achieve excellent PCEs of 25.38%, 20.59%, and 17.87%, respectively. This work offers a rational molecular design strategy for advancing high-performance and stable PSCs.