Boosting Charge Transport in a 2D/3D Perovskite Heterostructure by Selecting an Ordered 2D Perovskite as the Passivator

We demonstrate that an ordered 2D perovskite can significantly boost the photoelectric performance of 2D/3D perovskite heterostructures. Using selective fluorination of phenyl-ethyl ammonium (PEA) lead iodide to passivate 3D FA(0.8)Cs(0.2)PbI(3), we find that the 2D/3D perovskite heterostructures passivated by a higher ordered 2D perovskite have lower Urbach energy, yielding a remarkable increase in photoluminescence (PL) intensity, PL lifetime, charge-carrier mobilities (phi mu), and carrier diffusion length (L-D) for a certain 2D perovskite content. High performance with an ultralong PL lifetime of approximate to 1.3 mu s, high phi mu of approximate to 18.56 cm(2) V-1 s(-1), and long L-D of approximate to 7.85 mu m is achieved in the 2D/3D films when passivated by 16.67 % para-fluoro-PEA(2)PbI(4). This carrier diffusion length is comparable to that of some perovskite single crystals (>5 mu m). These findings provide key missing information on how the organic cations of 2D perovskites influence the performance of 2D/3D perovskite heterostructures.