Shape-driven optimization strategy for efficient and stable lead-free all-perovskite tandem solar cells

Due to environmental concerns arising from the toxicity of lead-based perovskite solar cells (PSCs), developing efficient and stable lead-free perovskite solar cells has become a research hotspot. However, lead-free alternatives continue to struggle with high photovoltaic performance. In addition, despite the perovskite grain shape and structure plays a significant role in photon absorption, no significant dedicated research has been conducted to explore shape-driven photovoltaic properties of PSCs, so far. To fill this gap, we utilized COMSOL Multiphysics software to investigate the perovskite grain shape-modulated photovoltaic optimization aiming to systematically enhance the overall performance of lead-free all-perovskite tandem solar cells (APTSCs). Our findings proposed that perovskite grain with cylindrical shape exhibit excellent photovoltaic performance, as the single-junction lead-free devices with narrow and wide bandgap exhibited optimal power conversion efficiency (PCE) of 31.67 % and 21.15 %, respectively. Furthermore, we successfully constructed 2T lead-free perovskite tandem solar cells by combining the optimized single-junctions and PCE value as high as 33.28 % was achieved. These results not only demonstrate the enormous potential of lead-free perovskite materials but also validate that perovskite grain shape is a crucial parameter for light trapping in solar absorber materials which has the potential to effectively overcome the current material's limitations and can boost the device efficiency of lead-free perovskite tandem devices.