Robust and Tailored 1D/3D Heterojunction for Efficient and Stable Perovskite Solar Cells

ABSTRACT Operational stability remains a critical challenge for organic–inorganic hybrid perovskite solar cells (PSCs). Recently, the use of low‐dimensional perovskite has emerged as a promising route to enhance the device robustness. It is found that the 1D/3D heterojunction has a significant impact on the stability, while the role of spacer cations in the 1D/3D heterojunction regulation is poorly understood. Here, we report the synthesis of two new types of 1D perovskite single crystals, (BZ) ₂ Pb _1.5 I ₄ , (TFBZ)PbI ₃ , using benzamidinium (BZ) and (trifluoromethyl) benzamidinium (TFBZ) as spacer cations. Our analysis reveals that the trifluoromethyl groups in TFBZ contribute to extensive hydrogen‐bond networks and confer a high dipole moment. These features strengthen the interaction between TFBZ and inorganic [PbI ₆ ] ⁴⁻ skeleton, resulting in high structure stability and orientationally crystallized 1D perovskites. Furthermore, the incorporation of 1D (TFBZ)PbI ₃ forms a robust and high‐quality 1D/3D heterojunction interface, facilitated by stable 1D phase, favorable lattice matching, strong interface binding, and effective defect passivation. Accordingly, the resulting TFBZ‐based 1D/3D hybrid PSCs achieve a power conversion efficiency of 25.54%, while maintaining expectational operational and thermal stability. This work provides a design strategy to control the microstructure of a 1D/3D heterojunction, enabling highly efficient and stable perovskite photovoltaics.