Morphology and structure improvement of the hybrid CH3NH3PbI3 perovskite film via external doping

The optoelectronic properties of perovskite films are closely related to their quality. Herein, we report the doping of guanidinium iodide (C(NH2)3I) organic into CH3NH3PbI3 perovskite thin films and reveal the enhancement of both morphology and structure of the perovskite films by doping with C(NH2)3I in the range of 0 to 25%. Nuclear magnetic resonance is utilized to determine the molecular structure of the synthesized C(NH2)3I and grazing-incidence X-ray diffraction is employed to characterize the lattice structure of doped perovskite films. Furthermore, doped CH3NH3PbI3 perovskite films with different amounts of C(NH2)3I is also investigated by X-ray photoelectron spectroscopy and scanning electron microscopy. It is found that the C(NH2)3I dopant mainly assembles on the surface region of the pristine CH3NH3PbI3 perovskite film. In the end, 5% C(NH2)3I to CH3NH3PbI3 perovskite film is found to be the doping ratio resulting in the best film structure and surface morphology.