Deciphering the Impact of Aromatic Linkers in Self-Assembled Monolayers on the Performance of Monolithic Perovskite/Si Tandem Photovoltaic

Aromatic linker-constructed self-assembled monolayers (Ar-SAMs) with enlarged dipole moment can modulate the work function of indium tin oxide (ITO), thereby improving hole extraction/transport efficiency. However, the specific role of the aromatic linkers between the polycyclic head and the anchoring groups of SAMs in determining the performance of perovskite solar cells (PSCs) remains unclear. In this study, we developed a series of phenothiazine-based Ar-SAMs to investigate how different aromatic linkers could affect molecular stacking, the regulation of substrate work function, and charge carrier dynamics. When served as hole-selective layers (HSLs) in PSCs and monolithic perovskite/silicon tandem solar cells (P/S-TSCs), we found that the Ar-SAM with naphthalene linker along the 2,6-position axis (β-Nap) could form dense and highly ordered HSLs, enhancing interfacial interactions and favoring optimal energy level alignment with the perovskite films. Using this strategy, the optimized wide-band gap PSCs achieved an impressive power conversion efficiency (PCE) of 21.86 % with negligible hysteresis, utilizing a 1.68 eV perovskite. Additionally, the encapsulated devices demonstrated enhanced stability under damp-heat conditions (ISOS-D-2, 50 % RH, 65 °C) with a T₉₁ of 1000 hours. Notably, the fabricated P/S-TSCs, based on solution-processed micron-scale textured silicon heterojunction (SHJ) solar cells, achieved an efficiency of 28.89 % while maintaining outstanding reproducibility. This strategy holds significant promise for developing aromatic linking groups to enhance the hole selectivity of SAMs.