Molecular Hybrid Bridging for Efficient and Stable Inverted Perovskite Solar Cells without a Pre-Deposited Hole Transporting Layer.

Abstract

Establishing a low-resistance perovskite/ITO contact using self-assembled molecules (SAMs) is crucial for efficient hole transport in perovskite solar cells (PSCs) without a pre-deposited hole-transporting layer. However, SAMs at the buried interface often encounter issues like nonuniform distribution and molecular aggregation during the extrusion process, leading to significant energy loss. Herein, a molecular hybrid bridging strategy by incorporating a novel small molecule is proposed, (2-aminothiazole-4-yl)acetic acid (ATAA), featuring a thiazole ring and carboxylic acid group, along with the commonly used SAM, 4-(2,7-dibromo-9,9-dimethylacridin-10(9H)-yl)butyl)phosphonic acid (DMAcPA), into the perovskite precursor to synergistically optimize the buried interface. Composition analysis demonstrates that both molecules are effectively extruded to the bottom of the perovskite layer and form a well-oriented hole-selective contact interface through strong coordination between the anchoring groups and ITO substrate. The intermolecular interaction, along with the small molecular size of ATAA, enables its uniform dispersion among large DMAcPA, facilitating a compact molecular arrangement, effectively suppressing aggregation, and enhancing hole-transporting efficiency. As a result, the inverted PSC employing this molecular hybrid strategy exhibits a power conversion efficiency as high as 26.64% (certified at 26.34%) and maintains 98.5% of its initial efficiency after 1000 h of continuous operation under 1-sun illumination at the maximum power point.