Lattice matching propels customized-dimensionality 2D/3D perovskite heterojunctions for high-performance photovoltaics

2D/3D perovskite heterojunctions typically yield mixed-phase 2D perovskites, generating multiple quantum wells that impede charge transfer, thereby limiting the potential enhancement of solar cell efficiency. Here, we successfully fabricated phase-pure 2D (n = 2)/3D perovskite heterojunctions via introducing the γ-aminobutyric acid (GABA) ligand, which minimized energetic inhomogeneity, thus favoring interfacial charge transfer through optimized energy band alignment. The ligation between the oxygen atoms in the ligand and the uncoordinated lead in the 3D perovskite triggered a structural transition from cubic to tetragonal at the 3D perovskite surface, ensuring a seamless lattice matching with the 2D perovskite (n = 2), resulting in this optimized configuration. Utilizing this innovative structural configuration, the carrier properties of 2D/3D perovskite thin films have been significantly enhanced, exhibiting diffusion lengths exceeding 1000 nm and a mobility of 3.35 cm² V⁻¹ s⁻¹. Consequently, the fabricated small-area perovskite solar cells exhibited an impressive power conversion efficiency (PCE) of 25.06 %, while the mini-modules (10 cm × 10 cm) attained a maximum PCE of 17.27 %. Furthermore, the passivation of the 2D perovskite layers, coupled with their inherent superior resistance, enabled the unencapsulated target device to maintain outstanding long-term stability, even under challenging environmental conditions of light, heat, and humidity.