Molecular Engineering of Terminus, Conjugation, and Energetics for Thermally Stable Inverted Perovskite Solar Cells

Low-dimensional (LD)/three-dimensional (3D) heterostructure perovskite solar cells (PSCs) have achieved a power conversion efficiency (PCE) greater than 26%. However, the use of some ionic interfacial passivation materials in the construction of LD perovskites compromises device stability, as they can induce ion diffusion, particularly under high temperatures and light stress. In this study, we substitute the ammonium terminus (R-NH₃⁺) of conventional passivators with a carbamate terminus (R-NH-(CO)OR) and synthesized carbamate molecules featuring phenyl (PEA-Boc) and naphthalimide (ND-Boc) scaffolds. Through modulating the ionic terminus and enlarging the conjugated backbone of the passivation materials, the interlayer diffusion across PSCs was effectively inhibited. Moreover, the ND-Boc with electron-accepting moieties optimizes the band energy alignment, reduces defect density, and facilitates interfacial electron transfer of PSCs. As a result, the small-area target PSCs (0.04 cm²) and mini-modules (aperture area of 15.45 cm²) achieved a PCE of 26.04% and 21.83%, respectively. Notably, the encapsulated ND-Boc-based PSC maintained 96.7% of its initial PCE after being tracked at a maximum power point for 1500 h at 85 °C under argon (ISOS-L-2I protocol). Our strategy offers a simple and generally applicable passivation method for fabricating efficient and robust PSCs to facilitate their practical applications.