Optical properties of organic/inorganic perovskite microcrystals through the characterization of Fabry–Pérot resonances

A precise knowledge of the optical properties, specifically the refractive index, of organic/inorganic perovskites, is essential for pushing forward the performance of the current photovoltaic devices that are being developed from these materials. Here we show a robust method for determining the real and the imaginary part of the refractive index of MAPbBr3 thin films and micrometer size single crystals with planar geometry. The simultaneous fit of both the optical transmittance and the photoluminescence spectra to theoretical models defines unambiguously the refractive index and the crystal thickness. Because the method relies on the optical resonance phenomenon occurring in these microstructures, it can be used to further develop optical microcavities from perovskites or from other optical materials.

Fig. 1. Schematic representation of the Optical Transmission and PL experiments

Fig. 2. Differences in the spectra because of the effect of the numerical aperture (NA). Calculations/Simulations

Fig. 4 (a) Optical microscopy image of the measured MAPbBr3 crystal microcavity (square structure at the center of the image). (b) and (c) Experimental data and fitted curves for the OT and the PL spectra respectively. Resonant modes are indicated on top of their resonance peak by their mode-order, m. (d) Real and (e) imaginary part of the fitted refractive index and that of ref. 27. for comparison. (e) Finesse and (f) Quality Factor for all of the identified modes. The lines act as a guide to the eye.