Fig. 3. Near-field spectra s2(perovskite)/s2(Au) of CH3NH3PbI3 polycrystalline film (s2,IG/s2,Au at position A and s2,GB/s2,Au at position B marked in Fig. 1b).
The solid lines show calculations performed with the finite dipole model of s-SNOM, using a probe with tip-radius of 25 nm and tip-tapping amplitude of 60 nm. The charge mobility and dielectric data for CH3NH3PbI3 are taken from the literatures;2,51 and the free-carrier density n is the fitting parameter. The best agreement between the calculations and the experiments on CH3NH3PbI3 was found for a free-carrier density n = 6 × 1019 cm−3 at GB in the dark and n = 8 × 1019 cm−3 at GB under 532 nm laser illumination