Reconstruction of the Surface for Efficient 3D/Quasi-2D Heterostructured Inverted Perovskite Solar Cells

Abstract

Energy level misalignment-induced interfacial non-radiative recombination and interface defect-induced carrier transport loss are key factors limiting the power conversion efficiency (PCE) of perovskite solar cells. To address these issues, this work introduces 3-Piperidinecarboxamide (PDN) to reconstruct the surface of the 3D perovskite. PDN passivates both shallow and deep defects simultaneously, forming an n-type quasi-2D perovskite surface layer that enhances electron extraction and reduces the energy level barrier. Density functional theory (DFT) calculations reveal that the electron donor unit (R-C-NH) of PDN preferentially binds to undercoordinated Pb²⁺ defects sites on the perovskite (PVK) surface. The hydrogen bonding formed between the R-NH₂ group of PDN and I⁻ ions on the [PbI₆]⁴⁻ octahedra enhances the above binding capability. The device adopting this strategy achieves a champion PCE of 26.10%. Furthermore, unencapsulated PSCs also exhibits excellent stability, retaining 88% of the initial PCE retained after ≈1400 h at 25 °C under 30% humidity.