Interplay between nucleation and crystal growth during the formation of CH3NH3PbI3 thin films and their application in solar cells

A series of nonpolar antisolvents (chlorobenzene, bromobenzene, iodobenzene and toluene) were used to assist in the formation of smooth and crystalline CH3NH3PbI3 thin films by a one-step spin-coating method. The structural, optical and excitonic characteristics of the resultant CH3NH3PI3 thin films were analyzed using an atomic-force microscope, X-ray diffractometer, absorbance spectrum, photoluminescence (PL) spectrum, time resolved PL and temperature-dependent PL. The properties of the CH3NH3PbI3 thin films are dependent on the relative polarity and boiling point of the nonpolar antisolvents used in the washing treatment process. The interplay between nucleation (relative polarity) and crystal growth (boiling point) during the formation of CH3NH3PbI3 thin films influences the short-circuit current density (J(sc)) and power conversion efficiency (PCE) of the corresponding solar cells. The experimental results demonstrate that iodobenzene can be substituted for toluene as a more efficient antisolvent in the washing treatment process during the fabrication of CH3NH3PbI3 thin films. In addition, it is predicted that the J(sc) and PCE can be further improved by increasing the crystallinity of the CH3NH3PbI3 thin film.