Supramolecular carboxylic acid complex elastomer for CsPbI_3-xBr_x-based perovskite solar cells with high efficiency and excellent stability

CsPbI_3-xBr_x-based perovskite solar cells (PSCs) have been developed as highly promising photovoltaic devices for both single-junction and tandem solar cell applications, owing to their outstanding thermal stability and tunable bandgap. Despite rapid advancements in power conversion efficiency (PCE), further progress has been hindered by intrinsic defects formed during crystallization. To obtain a high-quality and phase-stable perovskite film, we designed and synthesized a supramolecular carboxylic acid complex elastomer (TD-Eu) as a multifunctional dopant to regulate defects in perovskite films. Experimental results effectively demonstrate that the -COOH group in TD-Eu enhances the phase transition barrier by passivating uncoordinated Pb²⁺, while the Eu³⁺-Eu²⁺ pair effectively captures Pb⁰ and I⁰ defects through a continuous “redox shuttle” mechanism. Additionally, the hydrophobic network-like alkyl chains in TD-Eu inhibit moisture and oxygen immersion. Consequently, the champion TD-Eu-doped device demonstrates a PCE of 19.61 % and exhibits exceptional operational stability, retaining 94.6 % of its initial performance after 1008 h of continuous 1-sun illumination. This work not only demonstrates one of the highest reported light stabilities for CsPbI_3-xBr_x-based PSCs, but also introduces a novel material that provides a sustainable “three-in-one” effect of improving the phase stability toward commercial PSCs.