Optimizing 2D passivation for enhancing performance of fully air-processed carbon electrode-based perovskite solar cells

Abstract

Air-processed carbon-based perovskite solar cells (C-PSCs) offer scalable and cost-effective photovoltaic manufacturing but face efficiency loss compared to metal-contact perovskite solar cells. Surface passivation of three-dimensional (3D) perovskites with two-dimensional (2D) perovskite layers has emerged as a promising strategy to enhance device performance. However, the mechanisms by which 2D perovskites more effectively improve C-PSC efficiency and stability remain underexplored. This study investigates the efficacy of 2D/3D heterostructures using n-hexylammonium bromide (C₆Br), phenethylammonium iodide (PEAI), and n-octylammonium iodide (OAI) as surface passivators for C-PSCs. C-PSCs treated with C₆Br achieved a champion power conversion efficiency (PCE) of 21.0%. This enhancement is attributed to superior defect passivation, improved charge extraction, and suppressed non-radiative recombination. Transient ion-drift characterization demonstrates that C₆Br and OAI reduce ionic conductivity by 2–3 orders of magnitude, correlating with enhanced operational stability under continuous illumination. Our findings highlight the role of short-chain bromide cations (C₆Br) in optimizing halide-mediated defect healing and interfacial band alignment, positioning 2D-passivated C-PSCs as viable competitors to conventional metal-contact perovskite solar cells.