Chemical Strain Engineering of MAPbI_3 Perovskite Films

摘要

This study introduces a new chemical method for controlling the strain inmethylammonium lead iodide (MAPbI_3) perovskite crystals by varying theratio of Pb(Ac)_2 and PbCl_2 in the precursor solution. To observe the effecton crystal strain, a combination of piezoresponse force microscopy (PFM)and X-ray diffraction (XRD) is used. The PFM images show an increase inthe average size of ferroelastic twin domains upon increasing the PbCl_2content, indicating an increase in crystal strain. The XRD spectra supportthis observation with strong crystal twinning features that appear in thespectra. This behavior is caused by a strain gradient during the crystallizationdue to different evaporation rates of methylammonium acetateand methylammonium chloride as revealed by time-of-flight secondaryion mass spectroscopy and grazing incidince X-ray diffraction measurements.Additional time-resolved photoluminescence shows an increasedcarrier lifetime in the MAPbI_3 films prepared with higher PbCl_2 content,suggesting a decreased trap density in films with larger twin domainstructures. The results demonstrate the potential of chemical strain engineeringas a simple method for controlling strain-related effects in leadhalide perovskites.