Dual Bimolecular Passivation Strategy for Enhanced Efficiency and Stability in Perovskite Solar Cells via a Solution-Based Two-Step Process

Perovskite photovoltaics offer high power conversion efficiencies (PCEs) and low-cost manufacturing, making them a transformative solar technology. The solution-based two-step process has emerged as a promising method to deposit dense and pinhole-free perovskite top cells on silicon (Si) bottom cells. Commercial Si solar cells with microscale textures exhibit better light harvesting, paving the way for high-efficiency 2T perovskite/Si tandem solar cells (TSCs). However, long-term stability remains a major challenge for perovskite solar cells (PSCs). This study transitions from a triple cation (CsMAFA) to a double cation (CsFA) perovskite composition, achieving highly efficient PSCs with improved stability. Implementing a novel dual bimolecular passivation strategy for both bulk and surface passivation effectively addresses defects at grain boundaries and interfaces, resulting in a stable power output exceeding 20.9%. This represents the most efficient p-i-n type perovskite solar cell with a bandgap of 1.67 eV, processed by a two-step spin-coating method. Applied on textured Si bottom cells, this process achieves PCEs exceeding 24% for laboratory scale monolithic perovskite/Si TSCs.