Fabrication and Characterization of CH 3 NH 3 PbI 3− x − y Br x Cl y Perovskite Solar Cells

Fabrication and characterization of CH 3 NH 3 PbI 3− x − y Br x Cl y perovskite solar cells using mesoporous TiO 2 as electron transporting layer and 2,2′,7,7′-tetrakis-( N,N -di-4-methoxyphenylamino)-9,9′-spirobifluorene as a hole-transporting layer (HTL) were performed. The purpose of the present study is to investigate role of halogen doping using iodine (I), bromine (Br) and chlorine (Cl) compounds as dopant on the photovoltaic performance and microstructures of CH 3 NH 3 PbI 3− x − y Br x Cl y perovskite solar cells. The X-ray diffraction identified a slight decrease of crystal spacing in the perovskite crystal structure doped with a small amount of I, Br, and Cl in the perovskite compounds. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) showed the perovskite crystal behavior depended on molar ratio of halogen of Pb, I, Br and Cl. Incorporation of the halogen doping into the perovskite crystal structure improved photo generation, carrier diffusion without carrier recombination in the perovskite layer and optimization of electronic structure related with the photovoltaic parameters of open-circuit voltage, short-circuit current density and conversion efficiency. The energy diagram and photovoltaic mechanisms of the perovskite solar cells were discussed in the context of the experimental results.