Chemical Strain Engineering of MAPbI<sub>3</sub> Perovskite Films
Yenal Yalçinkaya, Ilka Hermes, Tobias Seewald, Katrin Amann‐Winkel, Lothar Veith, Lukas Schmidt‐Mende, Stefan A. L. Weber
Abstract
Abstract This study introduces a new chemical method for controlling the strain in methylammonium lead iodide (MAPbI 3 ) perovskite crystals by varying the ratio of Pb(Ac) 2 and PbCl 2 in the precursor solution. To observe the effect on crystal strain, a combination of piezoresponse force microscopy (PFM) and X‐ray diffraction (XRD) is used. The PFM images show an increase in the average size of ferroelastic twin domains upon increasing the PbCl 2 content, indicating an increase in crystal strain. The XRD spectra support this observation with strong crystal twinning features that appear in the spectra. This behavior is caused by a strain gradient during the crystallization due to different evaporation rates of methylammonium acetate and methylammonium chloride as revealed by time‐of‐flight secondary ion mass spectroscopy and grazing incidince X‐ray diffraction measurements. Additional time‐resolved photoluminescence shows an increased carrier lifetime in the MAPbI 3 films prepared with higher PbCl 2 content, suggesting a decreased trap density in films with larger twin domain structures. The results demonstrate the potential of chemical strain engineering as a simple method for controlling strain‐related effects in lead halide perovskites.