Fig. 4. Electronic energy band structures for CH₃NH₃MX₃ (where CH₃NH₃: MA; M: Cu, Zn, Ge, Sn, Pb; X = Cl, Br, I) in the high-symmetry direction, except for CH₃NH₃GaX₃ which is metallic in nature. The blue and red lines on the upper and lower sides of the Fermi level indicate the CBM and VBM, respectively.