Passivation-Induced Interfacial Fields Reshape Carrier-Extraction Landscapes in Perovskite Solar Cells

Abstract

Organic ammonium passivation is known to improve perovskite solar cells (PSCs) by modifying interfacial defects, energetics, and electrostatics, yet how these local interfacial changes manifest as spatial carrier-extraction pathways inside operating devices remains unclear. Here, we combine back-excitation transient reflection spectroscopy, cross-sectional photocurrent imaging, and drift–diffusion modeling to directly correlate interfacial modification with longitudinal carrier transport and spatial carrier extraction. Although phenethylammonium iodide (PEAI) and octylammonium iodide (OAI) are introduced at the hole-transport interface, both produce direction-dependent carrier transport across the absorber and enhance photocurrent generation near the remote electron-transport-layer interface. Drift–diffusion analysis shows that passivation shifts the intersection point of the electron and hole collection-probability curves toward the electron-transport layer (ETL), with OAI producing a more spatially extended interfacial field than PEAI. Our findings show that molecular passivation redistributes carrier-collection probabilities across the absorber, thereby enhancing extraction near the remote interface.