Investigation of chlorine-mediated microstructural evolution of CH3NH3PbI3(Cl) grains for high optoelectronic responses

An organic-inorganic hybrid perovskite is considered as a next generation solar energy harvester due to the high power conversion efficiency. The starting precursor solution for the organolead halide perovskite is of significant interests because the ionic components in the precursor can critically affect the nanostructures and thereby the optoelectronic properties. In this work, the basic and well-known precursor solution for CH3NH3PbI3(Cl) comprised of CH3NH3I and PbCl2, is specifically analyzed to unravel the phenomena in the Cl-mediated solutions. The shift in equilibrium between lead-halide complex and the solvent results into the CH3NH3PbI3(Cl) grain evolution with Cl incorporation, which is confirmed through x-ray fluorescence and diffraction. The effects of Cl on the optoelectronic properties are further verified by conductive atomic force microscopy, and the existing Cl leads to the 30-times-increased and inhomogeneously distributed photocurrent for CH3NH3PbI3(CI) grains compared with CH3NH3PbI3. Moreover, photocurrent noise from the mixed-halide perovskite is reduced than that from the triiodide perovskite phase. Combining the microstructural evolution with the optoelectronic properties of mixed halide perovskite, it is concluded that additional CI reduces the defects of recombination centers resulting high photocurrent. (C) 2016 Elsevier Ltd. All rights reserved.