An understanding of the effects of doping in lead perovskites may allow for improved solar cell performance or reduction in toxicity of the materials used. Ba 2+ doped CH 3 NH 3 PbI 3 (CH 3 NH 3 Pb 1−x Ba x I 3 with x = 1%, 5% and 10%) are successfully synthesized by cooling down a concentrated aqueous solution containing HI, CH 3 NH 2 and metal acetates and their properties are investigated using x-ray diffraction, differential scanning calorimetry, and impedance spectroscopy (IS). No new structures are formed upon doping with Ba 2+ ions, however the lattice expands. The IS measurements show a strong increase in the conductivity and dielectric constants of the doped crystals. The conductivity arises mainly from vacancy mediated iodide ion (I −) migration and the increase in ionic conductivity with dopants is ascribed to increased defect formation due to lattice distortion. In addition, the bulk dielectric constant increases with increasing Ba 2+ dopant. The increase in the dielectric constant is consistent with ordering of CH 3 NH 3 dipoles resulting from distortions of the Ba sites in the lattice. The temperature dependence of the dielectric constants is attributed to thermal effects on the orientation of CH 3 NH 3 molecules.
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