Hyperspectral mapping of nanoscale photophysics and degradation processes in hybrid perovskite at the single grain level

With solar cells reaching 26.1% certified efficiency, hybrid perovskites are now the most efficient thin film photovoltaic material. Though substantial effort has focussed on synthesis approaches and device architectures to further improve perovskite-based solar cells, more work is needed to correlate physical properties of the underlying film structure with device performance. Here, using cathodoluminescence microscopy coupled with unsupervisedmachine learning, we quantify how nanoscale heterogeneity globally builds up within a large morphological grain of hybrid perovskite when exposed to extrinsic stimuli such as charge accumulation from electron beams or milder environmental factors like humidity. The converged electron-beam excitation allows us to map PbI2 and the emergence of other intermediate phases with high spatial and energy resolution. In contrast with recent reports of hybrid perovskite cathodoluminescence, we observe no significant change in the PbI2 signatures, even after highenergy electron beam excitation. In fact, we can exploit the stable PbI2 signatures to quantitatively map how hybrid perovskites degrade. Moreover, we showhow ourmethodology allows disentangling of the photophysics associated with photon recycling and band-edge emission with sub-micron resolution using a fundamental understanding of electron interactions in hybrid perovskites.

Automated summary

Researchers used cathodoluminescence microscopy and unsupervised machine learning to study how nanoscale heterogeneity accumulates within the structure of hybrid perovskite under external stimuli. They found that there was no significant change in the performance of hybrid perovskite under high-energy electron beam excitation, which can be used to study its degradation process.