Relationship between Lattice Strain and Efficiency for Sn-Perovskite Solar Cells

In the composition of Q(0.1)(FA(0.76)MA(0.25))(0.9)SnI3, Q is replaced with Na+, K+, Cs+, ethylammonium(+) (EA(+)), and butylammonium(+) (BA(+)), respectively, and the relationship between actually measured lattice strain and photovoltaic performances is discussed. The lattice strain evaluated by the Williamson-hall plot of X-ray diffraction data decreased as the tolerance factor was close to diffraction data decreased as the tolerance factor was close to one. The efficiency of the Sn-perovskite solar cell was enhanced as the lattice strain decreased. Among them, EA(0.1)(FA(0.75)MA(0.25))(0.9)SnI3 having lowest lattice strain gave the best result of 5.41%. Because the carrier mobility increased with a decrease in the lattice strain, these lattice strains would disturb carrier mobility and decrease the solar cell efficiency. Finally, the results that the efficiency of the SnGe-perovskite solar cells was gradually enhanced from 6.42 to 7.60% during storage, was explained by the lattice strain relaxation during the storage.