Growth behaviors and emission properties of Co-deposited MAPbI3 ultrathin films on MoS ₂

Hybrid organic–inorganic perovskite thin films have attracted much attention in optoelectronic and information fields because of their intriguing properties. Due to quantum confinement effects, ultrathin films in nm scale usually show special properties. Here, we report on the growth of methylammonium lead iodide (MAPbI ₃) ultrathin films via co-deposition of PbI ₂ and CH ₃NH ₃I (MAI) on chemical-vapor-deposition-grown monolayer MoS ₂ as well as the corresponding photoluminescence (PL) properties at different growing stages. Atomic force microscopy and scanning electron microscopy measurements reveal the MoS ₂ tuned growth of MAPbI ₃ in a Stranski–Krastanov mode. PL and Kelvin probe force microscopy results confirm that MAPbI ₃/MoS ₂ heterostructures have a type-II energy level alignment at the interface. Temperaturedependent PL measurements on layered MAPbI ₃ (at the initial stage) and on MAPbI ₃ crystals in averaged size of 500 nm (at the later stage) show rather different temperature dependence as well as the phase transitions from tetragonal to orthorhombic at 120 and 150 K, respectively. Our findings are useful in fabricating MAPbI ₃/transition-metal dichalcogenide based innovative devices for wider optoelectronic applications.