New Paper: Designing Bifunctional Passivation Molecules

Mitigating non-radiative recombination at the perovskite/C60 interface is critical for achieving high-efficiency perovskite solar cells. A common strategy relies on small organic, mostly amino- or ammonium-functionalized molecules as interfacial layers. Combining these functionalities with carboxylic or phosphonic acids offers a route to target multiple defect types, yet design principles for such bifunctional molecules remain poorly understood. In this study, we developed a design framework by systematically varying the functional groups of such molecules. By combining density functional theory, optoelectrical device simulations, and experiment, we linked molecular functionality to passivation mechanism, device performance, and stability. While diammonium functionality primarily induces field-effect passivation, phosphonic and carboxylic acids enable chemically selective defect passivation. Furthermore, diammonium-based interlayers deliver strongest recombination suppression. In contrast, carboxylic acid-based devices show superior stability, revealing a trade-off between passivation strength and operational stability, offering future guidelines for rational design of passivation molecules.

https://doi.org/10.1039/d6ee02985j