A perovskite solar cell, that was first reported by Miyasaka et al. in 2009, has recently received much attention.¹⁾ The organic-inorganic perovskite, RNH₃PbX₃ (X = Cl, Br, I), can function as a light absorption layer. Power conversion efficiency (PCE) of the perovskite solar cell is getting >15%, better than those of OPV and DSSC.^2,3) A device of the perovskite solar cell is solution-processible enabling fabrication at low cost. The organic-inorganic perovskites RNH₃PbX₃ are easily prepared from HX salts of organic amines and lead halides. A modification of the halide X in the (MeNH₃)PbX₃ can control the range of absorption wavelength. The perovskite compound with X = Br is useful for light absorption in shorter wavelengths and the compound with X = I is relatively useful for that in longer wavelengths. Wakamiya et al. reported that use of highly dried lead(II) iodide [L0279] is a key to fabricate efficient perovskite solar cell devices (PCE > 10%) with high reproducibility.^4,5)