Tailoring Heterojunction Energetics for 3D/2D Bilayer Stack Perovskite Solar Cells

Energetics mismatch at the 3D/2D heterojunction is one important source for nonradiative recombination in 3D/2D heterojunction perovskite solar cells (PSCs). Herein, we successfully tailor the energetics of bilayer stack 3D/2D heterojunctions via different interfacial dipoles employing a series of molecular interlayers and explore the impacts of energetics and conduction band minimum energy offsets at 3D/2D heterojunctions on electron extraction efficacy and operational stability for p-i-n PSCs. We reveal that the negative dipole efficiently eliminates the energetics mismatch at the 3D/2D heterojunction and accelerates the electron transport across the heterojunction. Furthermore, the improved energetics at the 3D/2D heterojunction inhibits halide ion migration, significantly improving the device long-term stability. As a result, we achieve an impressive and robust efficiency over 25%, among the highest performance reported to date for 3D/2D bilayer stack PSCs using direct deposition of 2D perovskite. This work offers a promising strategy of energetics management to push 3D/2D heterojunction PSC technology forward.