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Hybrid perovskite single-crystalline thin films are promising for making high-performance perovskite optoelectronic devices due to their superior physical properties. However, it is still challenging to incorporate them into multilayer devices because of their on-substrate growth. Here, a wet transfer method is used in transferring perovskite single-crystalline films perfectly onto various target substrates. More importantly, large millimeter-scaled single-crystalline films can be obtained via a diffusion-facilitated space-confined growth method as thin as a few hundred nanometers, which are capable of sustaining excellent crystalline quality and morphology after the transferring process. The availability of these crystalline films offers us a convenient route to further investigate their intrinsic properties of hybrid perovskites. We also demonstrate that the wet transfer method can be used for scalable fabrication of perovskite single-crystalline film-based photodetectors exhibiting a remarkable photoresponsivity. It is expected that this transferring strategy would promise broad applications of perovskite single-crystalline films for more complex perovskite devices.

The controllable biaxial strain is experimentally imposed on α-In2Se3 nanosheets by an electromechanical device. A redshift of Raman spectra is observed from the nanosheets under the strain. The Gruneisen parameter is calculated to analyze the strain effect on the vibrational behavior. Photoluminescence shows a blueshift, which can reach up to 215 meV per 1% strain. Such tunability of optical characteristics observed from α-In2Se3 nanosheets is much higher than that from conventional semiconductors. The physical mechanism behind the observation is investigated, which is related to the variations in the energy band and photoexcited carriers under a piezoelectric field and laser power.