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

Scientific Summary

This study investigates the efficacy of 2D perovskite passivation layers in enhancing the performance and stability of fully air-processed, carbon electrode-based perovskite solar cells (C-PSCs). The main goal was to compare n-hexylammonium bromide (C6Br), phenethylammonium iodide (PEAI), and n-octylammonium iodide (OAI) as passivators and elucidate the underlying mechanisms. Key findings reveal that C6Br-treated C-PSCs achieved a champion power conversion efficiency (PCE) of 21.0%, attributed to superior defect passivation, improved charge extraction, and suppressed non-radiative recombination. All 2D passivators improved PCE, with C6Br leading, followed by PEAI (19.7%) and OAI (17.6%). Critically, C6Br and OAI significantly reduced mobile ion concentration and ionic mobility by 2–3 orders of magnitude, directly correlating with enhanced operational stability. C6Br and OAI devices retained 100% initial efficiency over 500 hours under inert conditions, while OAI exhibited superior ambient stability, retaining 80%.

Why it Matters

These findings are crucial for advancing low-cost, scalable, and stable perovskite photovoltaic manufacturing. By demonstrating that specific 2D cations (especially C6Br and OAI) effectively suppress ionic conductivity, heal defects, and improve charge transport, this research provides actionable guidelines for molecular engineering of 2D/3D perovskite interfaces. This positions 2D-passivated C-PSCs as viable, efficient, and stable alternatives to conventional metal-contact PSCs, accelerating their commercialisation for sustainable energy applications.

Fluxim Tools Used

The PAIOS (Fluxim AG) all-in-one characterisation equipment was used to perform capacitance–voltage (C–V) measurements, electrochemical impedance spectroscopy (EIS), and dark J–V characterisation. PAIOS enabled a comprehensive analysis of the electrical properties of the devices, providing insights into the charge transport mechanisms and recombination processes. This included determining built-in potential from C-V Mott–Schottky plots, and extracting charge transfer resistance (Rct) and series resistance (Rs) from EIS Nyquist plots. The use of PAIOS was critical for correlating the observed improvements in PCE and stability with specific changes in device physics, such as enhanced charge separation and reduced trap states.

Publication Details

Khawaja, K.A., Vijayaraghavan, S.N., Penukula, S., Xiang, W., Rolston, N., Li, L. and Yan, F. (2025), Optimizing 2D passivation for enhancing performance of fully air-processed carbon electrode-based perovskite solar cells. EES Sol., 1, 620. https://doi.org/10.1039/d5el00099h.