Multiple functional bulk passivator pyrimidine derivative stabilizing perovskite precursors for efficient carbon-based perovskite solar cells.

Over the past few decades, perovskite solar cells (PSCs) have attracted great research attention attributed to their promising future as alternative energy sources. Even with exceptionally high power conversion efficiency (PCE) up to 27.3%, the chemical instability of perovskite precursors, induced by the undesirable transition of [PbI] octahedron and the high volatility of organic cations, is a big obstacle in achieving high efficiency and superior long-term stability of PSCs, thus restricting their industrial production and practical application. Herein, the stability of perovskite precursor solution was modulated by introducing a multifunctional passivator: ethyl-4-amino-2-mercapto-5-pyrimidinecarboxylate (AMPM). AMPM with electron-donating and electron-accepting groups can interact with perovskite precursor through coordination and hydrogen bonds. Thus, it effectively dissociates face- and edge-shared [PbI] octahedral aggregates, enhancing precursor colloidal dispersion, improving precursor stability and driving a reorganization into corner-shared [PbI]. Additionally, AMPM preferentially increases the relative abundance of higher-Miller-index (220) and (310) planes while preserving the predominance of the primary (110) facet, thereby reducing perovskite defect state density and improving charge extraction. As a result, compared with the control carbon-based PSCs (C-PSCs), the champion PCE of the C-PSCs was increased up to 18.48% AMPM treatment in perovskite bulk films. The PCE of the AMPM-treated C-PSCs retained 90% of the initial value after storage at 30-40% relative humidity for 50 days, compared with that of less than 47% for the original device. This research provides a novel approach to fabricate high-performance and durable perovskite-based optoelectronic devices by tuning the properties of the precursor materials colloidal chemistry.