Organic-inorganic hybrid perovskites are nowadays considered as reference materials for optoelectronics and photovoltaics. Their outstanding yields in luminescence, electroluminescence and photoelectric conversions, combined with the easy solution processing, promise large-scale production, wide dissemination and high technological throughput.

However, the well-known structural instability of hybrid perovskites under working conditions limits a real market uptake of all the related technologies. Solutions to guarantee the durability of products are mandatory and can be numerous, if the problem is addressed from different perspectives. 

Moreover, the plethora of perovskite materials produced in different laboratories, with preparation procedures changing from lab to lab and from time to time, ask for stabilising  treatments that, in a certain extent, reset the starting conditions in a convenient and reproducible manner. This is particularly needed for small grained perovskite layers, on one hand used to implement pinhole-free coverages, but, on the other hand, offering extended lattice discontinuities due to the high surface to volume ratio. In addition to morphology and environment, temperature-related effects are unavoidable during device operation. A rationalization of the phenomena needs to embody heating and thermal cycles to preserve the material integrity and/or the structural reversibility vs. temperature.

In this framework and on the basis of experiment and theory, we draw a general paradigm that reconsiders N₂ not simply being an inert species but rather a small effective healing gas molecule inside a MAPbI₃ layer. Nitrogen is soaked into polycrystalline MAPbI₃ via a post-deposition mild thermal treatment under slightly overpressure conditions in order to promote its diffusion through the whole layer. We observe a significant reduction of radiative recombination and a concurrent increase of light absorption, with a maximum benefit at 80 °C. Concomitantly, the current of holes locally drawn from the surfaces by a biased a tip with nanometric resolution has increased by a factor 3 under N₂. This was framed by a reduction of the barrier for the carrier extraction. The achieved improvements were linked to a nitrogen-assisted recovery of intrinsic lattice disorder at the grain shells along with a simultaneous stabilization of under-coordinated Pb^₂₊species and MA⁺ cations through weak electrostatic interactions. Defect mitigation under N₂ is further supported by the behavior of the absorption coefficient during thermal cycles in comparison to similar data under Argon. We additionally unveil that surface stabilization through N₂ is morphology-independent and can be thus applied after any preparation procedure.

Such simple and low-cost strategy could complement other stabilizing solutions when building perovskite solar cells or light-emitting diodes.

Paper just accepted in Advanced Energy Materials