Split-Standing Molecular Engineering for Textured Silicon/Perovskite Tandems

To effectively minimize reflection losses and achieve compatibility with industrial-scale silicon production lines, textured silicon/perovskite tandem solar cells have garnered significant attention in recent research. However, achieving uniform and stable coverage of the textured silicon substrate with hole-selective layer (HSL) remains a significant challenge. Herein, a HSL material, DPAICz ((indolo[2,3-a]carbazole-11,12-diylbis(ethane-2,1-diyl))bis(phosphonic acid)), is reported specifically designed for textured silicon substrate. Compared to the typical HSL material 2PACz, DPAICz features a π-expanded conjugated core and multiple anchoring groups, forming a split-standing configuration with anchoring groups positioned on opposite sides, resulting in superior anchoring stability on textured substrate under external stimuli. Moreover, DPAICz exhibited a larger molecular dipole moment and a more pronounced p-type characteristic, enhancing the interfacial hole extraction efficiency. Consequently, wide-bandgap (1.68 eV) perovskite solar cells employing DPAICz as the HSL achieved a champion power conversion efficiency (PCE) of 23.42%. Introducing the DPAICz into monolithic silicon/perovskite tandem solar cells greatly improved their performance, achieving a remarkable PCE of 32.55% in 1 cm² area. Importantly, the unencapsulated tandems based on DPAICz exhibited significantly enhanced long-term operational stability, retaining 96% of its initial PCE after 880 h of continuous 1-sun light soaking at 45 °C under open-circuit condition.