Metal halide perovskites are emerging as a solution processed, high efficient photovoltaic technology. Hybrid perovskites offer very outstanding properties including high absorption coefficient, micron diffusion length and tunable bandgap. However, the stability of this class of material is still a key challenge for industrialization. With the aid of advanced imaging techniques, it is shown that perovskites are tolerant to structural defects  and they also present reversible and non-reversible degradation paths .
Efficient perovskite solar cells have been manufactured fulfilling industry requirements including large scale coating technique (doctor blading) and development of inks from non-toxic solvents . The morphology-performance dependence in perovskite films processed by spin and blade coating is investigated by co-local photoluminescence (PL) and photocurrent maps (see image). The blade coated perovskite from non-toxic solvents leads to spherulitic growth which is shown to be beneficial for the device performance. The chemical defects are located at the grain boundaries of the spherullites and do not have detrimental impact on the photogenerated charges. 
Moreover, the degradation of the perovskite solar cells at the nanoscale level is addressed by comparing the photoconductive atomic force microscopy and photoluminescence maps. Two different degradation mechanisms are clearly identified: fully reversible behavior within the bulk of the perovskite crystal grains and a non-reversible degradation confined at the perovskite grains boundaries. Additionally, the movement of a degradation front is detected, from the boundaries towards the bulk of the grains. The study suggests that, in order to improve the perovskite stability, grain boundaries need to be minimized or passivated. 
 Defect tolerant perovskite solar cells from blade coated non-toxic solvents
Journal of Material Chemistry A, 6, 19085-19093 (2018)
 Topological distribution of reversible and non-reversible degradation in perovskite solar cells
Nano Energy, 45, 94-100 (2018)
Comparison between photoluminescence shift map for spin coated and bade coated perovskite solar cells. Statistical distribution of the data for the same spin coated (red line) and blade coated (green line) devices presented in the images