Growth and Application of MAPbI Single-Crystal Films through LIPSS on an ITO Surface.

Metal halide perovskite has attracted great interest as a promising optoelectronic device material due to its inherent excellent photoelectric properties. Currently, perovskites have made significant strides in enhancing their efficiency, yet their industrial advancement and multiscenario applications remain hampered by manufacturing technology. In this work, high-quality MAPbI single-crystal films were prepared through low spatial frequency laser-induced periodic surface structures (LIPSS) with a depth of 139 nm on the surface of ITO processed by femtosecond laser. Femtosecond laser processing revealed that the period of LIPSS decreases with the increase of laser fluence and increases with the increase of scanning speed. Meanwhile, the depth of LIPSS grows with increasing laser fluence and first ascends and then descends as scanning speed goes up. Ultrafast pump probe experiments revealed that the coulomb explosion dominated the interaction mechanism between the femtosecond laser and material at low laser fluence, while the phase explosion became the main mechanism at high laser fluence. The LIPSS with a depth of 139 nm was selected as the substrate to prepare MAPbI single-crystal films based on the spatially confined growth method as it greatly facilitates the light absorption rate of MAPbI single-crystal films by FDTD simulation. SEM, EDS, and XRD analyses proved that the MAPbI single-crystal films have excellent surface quality morphology and uniform element distribution. The average lifetime of an MAPbI single crystal obtained by time-resolved photoluminescence spectroscopy is about 24.05 ns, which indicates the low defect density and a long carrier lifetime in MAPbI single-crystal films. Transient absorption spectroscopy revealed that Auger recombination is the primary carrier recombination mode at high excitation fluence, which proposed a strong carrier band filling effect and energy structure with two conduction bands in MAPbI single-crystal films. The accumulated carriers promoted the excited-state absorption and slowed down the recombination, which is meaningful for the further application of MAPbI single-crystal films in optoelectronic devices.