Crown Ether-Modified 1D/3D Heterojunction for Efficient and Stable Carbon-Based CsPbI₃ Perovskite Solar Cells

Interface engineering strategies passivate defects on the polycrystalline perovskite film surface and improve the stability of corresponding perovskite solar cells (PSCs). However, a single interface engineering step can result in restricted benefits on various occasions. Therefore, an appropriate additional modification step can be necessary to synergistically improve the device performance. In this study, a two-step interface engineering strategy is developed. Initially, the CsPbI₃ perovskite surface is modified by choline iodide (ChI) to construct a 1D ChPbI₃/3D CsPbI₃ heterojunction, and then an additional surface modification step with the use of crown ether is applied. The crown ether modification can further eliminate unpassivated surface defects after heterojunction construction. Benefiting from the inhibited interfacial recombination, the resultant carbon-electrode-based CsPbI₃ PSCs (C-PSCs) deliver a champion efficiency of 18.78%, representing one of the highest levels in this field. Besides, crown ether can synergistically improve the stability of the device against moisture, heat, and light stress due to the enhanced hydrophobicity and suppressed ion migration.