Impact of reabsorption on the emission spectra and recombination dynamics of hybrid perovskite single crystals

International audienceA better understanding of the surface and bulk photophysics of hybrid perovskite is crucial to improve the efficiency of devices. The study of high quality single crystals should enable to highlight the intrinsic properties of hybrid organic-inorganic perovskites (HOPs). However, there are important discrepancies in the literature regarding the basic optical properties of HOP single crystals, such as the emission spectra. Here, we have investigated the surface and bulk properties of CH3NH3PbBr 3 single crystals with a combination of cathodoluminescence (CL), steady-state and time-resolved photoluminescence (PL) spectroscopy. Firstly, depth-resolved CL has been used to probe the near surface region on depth ranging from a few nanometers to several micrometers. Secondly, we have studied the transmitted PL through different thicknesses between 50 and 600 µm. In both cases, experimental emission spectra were compared with simulated spectra, taking into account reabsorption effect. The results reveal the strong impact of reabsorption on the emission of hybrid perovskites. Reabsorption effect explains mainly the large variation of the emission spectra reported for hybrid perovskite single crystals, as well as the existence of two PL peaks at room temperature. In addition, we show that hybrid perovskite single crystals, even with millimeter size, are partially transparent to their own luminescence and radiative transport is the dominant mechanism for the propagation of the excitation in thick crystals The transmitted PL presents a long rising time and a lengthening of its decay due to photon recycling and light-trapping. This project has received funding from the European Union’s Horizon 2020 programme, through a FET-Open research and innovation action under the grant agreement No 687008