Metal halide perovskite (MHPs) solar cells represent a promising newcomer in the front of emerging photovoltaic technologies, therefore a potential player to challenge the dramatic energy crisis and climate change that we are facing. The exceptional properties of MHPs derive from their hybrid organic-inorganic nature, which allows also for low-cost and straightforward processing. Solar cells containing MHPs as absorbing layer have already achieved a power conversion efficiency above 26,5 %, close to the efficiency of silicon-based devices. Nevertheless, a major limitation, still preventing the uptake of the technology, is related to the reduced stability of these devices when exposed to operative conditions, namely temperature, light, and moisture. Herein, an effective defect passivation of MHP surfaces is a key strategy to tackle both the stability and the enhancement of solar cell performances. Although many solution-based approaches have been tested, we have explored in the last years an innovative use of plasma, as a solvent-free, scalable, industrially available and non-invasive processing to enhance MHP solar cells performances [1]. The effect of cold plasmas fed by gases as Ar,  ,  and  both on lead-based (MAPbI3) [2] and lead-free (FASnI3) [3] perovskites was investigated in terms of optochemical and morphological modifications and correlated to the performance of the photovoltaic devices. An interesting improvement in power conversion efficiency (PCE) was observed for the Ar-treated MAPbI3 perovskites, ascribed to a modulation of surface defects, while a newsworthy suppression of the intrinsic tendency of tin (II) to oxidize to tin (IV) was obtained for the N2-plasma treated FASnI3 perovskites. Starting from these encouraging results, further surface plasma processes have been investigated [4], among which the promising treatment with sulfur-containing molecules, proved to obtain a good passivation of surface defects, through the formation of Pb-S bonds, allowing the improvement of both the fill factor and the PCE of the investigated solar cells, opening new applicability scenarios for these plasma-based processes [5]. 

References:

[1] V. Armenise, S. Covella, F. Fracassi, S. Colella, and A. Listorti, ‘Plasma‐Based Technologies for Halide Perovskite Photovoltaics’, Solar RRL, 2024, doi: 10.1002/solr.202400178.

[2] A. Perrotta et al., ‘Plasma-Driven Atomic-Scale Tuning of Metal Halide Perovskite Surfaces: Rationale and Photovoltaic Application’, Solar RRL, 2023, doi: 10.1002/solr.202300345.

[3] S. Covella et al., ‘Plasma-Based Modification of Tin Halide Perovskite Interfaces for Photovoltaic Applications’, ACS Applied Material & Interfaces, 2024, doi: 10.1021/acsami.4c09637.

[4] V. Armenise, S. Colella, A. Milella, F. Palumbo, F. Fracassi, and A. Listorti, ‘Plasma-Deposited Fluorocarbon Coatings on Methylammonium Lead Iodide Perovskite Films’, 2022, doi: 10.3390/en15134512.

[5] S. Covella et al., manuscript in preparation.