Graded Supramolecular Frameworks for Extending Space-Charge Modulation Regions and Boosting Carrier Dynamics in Perovskite Solar Cells.

Abstract

Efficient carrier separation and transport in perovskite solar cells are fundamentally constrained by the narrow space-charge regions intrinsic to conventional device architectures, leaving thick perovskite bulks electrically inactive. Here, we report a supramolecular graded electrostatic potential modulation strategy enabled by a fluorine-functionalized porous aromatic framework (PAF-2F) that spatially redistributes space charge throughout the perovskite absorber. The graded incorporation of PAF-2F continuously modulates the local electronic structure throughout the perovskite bulk, establishing an extended electrostatic potential gradient and transforming carrier transport from diffusion-dominated motion into field-assisted drift. This extended internal field accelerates charge separation, suppresses nonradiative recombination, and enhances charge extraction, yielding a champion power conversion efficiency of 26.66%. Moreover, the rigid conjugated framework and strong interfacial interactions of PAF-2F stabilize the graded doping profile and inhibit ion migration, resulting in excellent operational stability with 93% efficiency retention after 1000 h of continuous illumination without encapsulation. This work presents a general supramolecular strategy for bulk electronic structure engineering in perovskite semiconductors, offering a viable pathway toward simultaneously achieving high efficiency and long-term stability.