Doping modification of stannic perovskite based thin films for solar cell applications

The plumbic and stannic perovskite solar cell materials such as CH3NH3SnI3 and CH3NH3PbI3 were obtained by one step preparation with the surface morphology, microstructure, spectral absorption and device performance were investigated respectively. The spectral absorption of stannic perovskite material were found to expand wider and have an obvious red-shift compared to plumbic perovskite, with the absorption edge increased from 800 to 950 nm and the optical band gap reduced from 1.45 to 1.21 eV. But the conversion efficiency of stannic perovskite solar cell demonstrated significantly lower than that of plumbic perovskite, 2.05% and 6.71% respectively, due to a downshift of absorption intensity. However, bromine (Br) doping could broaden the band gap and thus give rise to the open circuit voltage of solar cell device accordingly. As the doping content increased from 0 to be totally replacement of iodine, the color of stannic perovskite turned gradually from dark brown to yellow, and the optical band gap increased up to 1.95 eV. At the same time, a blue shift of spectra absorption was observed, reducing from 950 to 650 nm. Noteworthy is that the solar cell conversion efficiency increased from initial 2.05% to 2.94% at the doping content of 0.5.