Suppressing Adsorption Disorder of Self‐Assembled Molecules for Efficient Perovskite/Silicon Tandem Solar Cells

ABSTRACT Realizing homogeneous assembly of self‐assembled molecules (SAMs) on NiO x is crucial for perovskite/silicon tandem solar cells (TSCs). However, the orientation of the spin‐coated SAM layer is always disordered. Herein, we report a dual strategy combining thermodynamic suppression of SAMs’ adsorption disorder through molecular design and kinetically overcoming molecular disorder via multi‐cycle deposition. Specifically, methoxy‐ (MeO‐) and methyl‐ (Me‐) substituted triphenylamine derivatives featuring a cyanovinyl phosphonic acid (CPA) anchoring group (MeOPA‐CPA and MePA‐CPA) are investigated. The study reveals that MePA‐CPA achieves a thermodynamically favored, well‐defined anchoring orientation on NiO x , characterized by a significantly higher adsorption energy for its anchoring group than its functional group. A multi‐cycle deposition strategy is employed to kinetically eliminate disordered physiosorbed overlayers and concurrently enhance SAMs’ coverage. This approach enables a dense and uniformly oriented SAM interlayer, significantly reducing non‐radiative recombination losses at the buried interface and enhancing the crystallinity and homogeneity of the subsequently deposited wide‐bandgap perovskite layer. Consequently, 1.68 eV perovskite solar cells deliver an efficiency of 23.91% and robust stability, retaining 90% of the initial efficiency after 1200 h of operation. The strategy enables perovskite/silicon TSCs with 31.17% efficiency, representing one of the most efficient perovskite/silicon TSCs based on planar silicon bottom cells.