Versatile perovskite solar cell encapsulation by low-temperature ALD-Al₂O₃ with long-term stability improvement

The outstanding advancement of perovskite solar cells (PSCs) in recent years makes them one of the currently most interesting topics in photovoltaic (PV) technology. However, some instability issues must be solved for future application. Encapsulation techniques have been an important solution to avoid or, at least, to limit those concerns for other PV technologies and are a promising way to circumvent extrinsic instability in the case of PSCs as well. Here, we introduce a low temperature (60 °C) encapsulation process based on a single thin coating of Al₂O₃ prepared by atomic layer deposition (ALD-Al₂O₃). Our procedure is compatible with the individual PSC components, and hence a mean of 93.6% of the original peak power conversion efficiency (PCE) was retained after encapsulation, with the champion device exhibiting a PCE of 17.4%. Moreover, the long term stability of the encapsulated devices was remarkably lengthened by preserving the fill factor and reducing the hysteresis usually observed in non-encapsulated samples. The improvements due to the ALD-Al₂O₃ encapsulation process were achieved for a standard PSC configuration: methylammonium lead triiodide (MAPbI₃), additivated-Spiro-OMeTAD and porous TiO₂ and could rapidly be extrapolated to other, more stable PSC architectures, paving a route towards commercialization.