(Invited) Progresses on Plasma Processing of Halide Perovskite Materials for Photovoltaic Applications
Authors: Covella Sara , Armenise Vincenza , Perrotta Alberto , Palumbo Fabio , Milella Antonella , Fracassi Francesco , Russo Francesca , Colella Silvia , Listorti Andrea 
Published: August 2024

Metal halide perovskite (MHPs) solar cells represent a promising newcomer in the front of emerging photovoltaic technologies to address 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 of about 25,7 %, 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 materials 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 1 have been tested, we propose here an innovative use of plasma, as a solvent-free, scalable, and non-invasive promising strategy to boost MHP solar cells performances 2. As starting point we exposed the surface of Methylammonium Lead Iodide perovskite thin films to different plasma conditions implying the variation of power, gas, and treatment time, both for low-pressure (LP) and atmospheric pressure plasmas (APPs). The impact of Ar, , and LPPs on MAPbI3
optochemical properties and morphology was correlated to the performance of the photovoltaic devices and rationalized by density functional theory calculations3. Herein an interesting improvement in photoluminescence was observed for the Ar and treated films, while an improvement in PCE was observed only for the Ar treated device. This result was ascribed to the efficient removal of the superficial organic component, revealed through X-ray photoelectron spectroscopy (XPS), following suitable surface passivation by the electron transporting layer deposition. Following these results, we tested APP treatments, finding a milder morphological modification than LPP treatments but withstanding good surface passivation, as confirmed through the improved photoluminescence intensity, while the effect in terms of photovoltaic devices is still under investigations. Moving from these encouraging results, we applied plasma surface treatments to tin-based perovskite, finding a very interesting beneficial effect when reductive plasma conditions (forming gas) were used on FaSnI3 thin film.4 The collection of these results already show the great versatility and potential of plasma-based techniques for the intelligent modification of metal halide perovskite for solar energy conversion.

References:

Han, T. H. et al. Interface and Defect Engineering for Metal Halide Perovskite Optoelectronic Devices. Advanced Materials
31, (2019).

Armenise, V. et al. Plasma-Deposited Fluorocarbon Coatings on Methylammonium Lead Iodide Perovskite Films. Energies (Basel)
15, 4512 (2022).

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

Covella S. et al. under preparation

Figure 1