Cyclohexylmethylammonium iodide-based bilateral interface engineering for efficient perovskite solar cells with improved stability and negligible hysteresis

Abstract

In perovskite solar cells, not only does the upper surface of the perovskite active layer affect device performance, but also the perovskite buried interface matters. In this work, we report an effective double-sided treatment strategy for passivating perovskite so as to fabricate efficient n–i–p solar cells with improved stability and negligible hysteresis. The strategy involves the simultaneous application of cyclohexylmethylammonium iodide (CMI) to modify both the upper perovskite/spiro-OMeTAD interface and the buried SnO₂/perovskite interface. It is demonstrated that the strategy significantly enhances the photovoltaic efficiency and stability of perovskite solar cells through synergistic dual-interface engineering. The buried-interface CMI promotes three-dimensional (3D) perovskite crystallization while reducing grain boundaries and defects, whereas the surface CMI modification generates two dimensional (2D)–3D perovskite heterostructures that are instrumental in passivating defects and improving carrier extraction at the perovskite/hole transport layer interface. The best-performing device, which underwent the double-sided CMI treatment, achieved a power conversion efficiency of 20.66% with improved stability and negligible hysteresis, substantially superior to those without CMI treatment or with single-sided CMI treatment only. The double-sided synergistic passivation strategy developed in this work offers a simple and effective approach to enhancing the device performance of perovskite solar cells.