 The crystal structures, elastic and anisotropic properties of CH3NH3BX3, B equals SN, PB, X equals BR, I, compounds as solar cell absorber layers were investigated using first principles calculations. The type and strength of chemical bonds between B and X atoms determined the elastic properties of these compounds. Organic cations and inorganic ions were also found to be important factors in determining the functionality of these absorbers. Bulk, shear, and Young's Moduli range from 12 to 30 gPa, 3 to 12 gPa, and 15 to 37 gPa, respectively. Additionally, the interactions among organic and inorganic ions had little effect on the elastic properties of these compounds. The B slash G ratio and Poisson's ratio showed that the perovskite material was highly ductile and could be used as a flexible or stretchable layer on a polymer substrate. This was due to its low shear modulus and strong anisotropy, which was derived from the elastic constants, chemical bonds, and symmetry. This article was authored by Jing Feng. We are article.tv, links in the description below.