Mapping photophysics properties of 3D and 2D-layered hybrid perovskites for energy-conversion applications*

Hybrid organic-inorganic perovskites have emerged as attractive solution-processed semiconductors for energy-conversion applications. With solar cells reaching 26 percent certified efficiency, they are now the most efficient thin-film photovoltaic material, and are also touted for other technologies such as light-emitting diodes, nanoscale lasers and detectors.  

In this talk, we discuss the fundamental photophysical processes that have enabled these materials to be such efficient light absorbers and charge collectors. At present, a major obstacle to further improve performance in compact devices is to pinpoint the role of heterogeneity in modifying carrier dynamics. Here we describe our efforts at the University of Alabama at Birmingham to determine the role of microstructure in dictating the photophysics and optoelectronic properties of hybrid perovskites on femtosecond timescale and at nanometer length scale. First, using pump-probe broadband microscopy, we probe the ultrafast dynamics of carriers in large-grain thin films, highlighting the detrimental effects of boundaries and interfaces. Second, using cathodoluminescence-enabled electron microscopy coupled with machine learning techniques, we discuss a method to quantify nanoscale heterogeneity within a single large-grain thin film of hybrid perovskite,  that is with spatial resolution well below the optical diffraction limit. This combined methodology allows us to disentangle complex hyperspectral datasets and create maps of various photophysical processes in hybrid perovskites, such as photon recycling and band-edge emission.