(Invited) Plasma Processes on Metal Halide Perovskite Interfaces for Photovoltaic Applications
Authors: Listorti Andrea , Covella Sara , Perrotta Alberto , Russo Francesca , Palumbo Fabio , Milella Antonella , Armenise Vincenza , Fracassi Francesco , Rizzo Aurora , Colella Silvia 
Published: September 2023

Metal Halide Perovskite (MHP) semiconductors are currently standing out for their exceptional optoelectronic properties and, particularly, for their exploitation in photovoltaics. Their structure can be described by the formula , where A is usually an organic cation, such as methylammonium (MA) or formamidinium (FA), B is a metal cation and X is a halogen anion, typically I or Br.
The exceptional properties of MHPs derive by their hybrid organic-inorganic nature, which also allows for low-cost fabrication processing. The raise of perovskite photovoltaics 1 followed progresses on three main research fronts: i) material deposition optimization, ii) material compositional tuning and iii) device interface engineering. The interfaces play a fundamental role in the device function affecting charge extraction, recombination processes and material/device overall stability. Therefore, to further improve the performances of these devices, many surface processes have been applied to solar cells interfaces, most of which include a solution-based methodology 2. The aim of these treatments is not only to improve solar cells efficiency in terms of carrier concentration and transport properties, but also to improve the device stability under working conditions, which is one of the main issues of these materials.
Among the different surface treatments exploitable, the use of plasma represents a solvent-free and non-invasive promising strategy to boost MHP solar cells performances. Plasma-deposited coatings on perovskite, as fluorocarbon polymers, have shown to improve material resistance to humidity and photoluminescence properties 3.
We have explored the effect of low-pressure plasmas fed with different gases, namely Ar, , and , on Metylammonium Lead Iodide surface4. An interesting improvement of perovskite photoluminescence and solar cell efficiency was observed for Ar and plasma treatments, ascribable both to the removal of organic components, proven to be beneficial to device performances 5, and to other chemical and morphological modifications depending on the gas used. Starting from these results, new plasma surface treatments, plasma-assisted deposition and encapsulation processes will be object of study of future research, to achieve a more complete understanding of the interfacial defects and charge carrier dynamics and to further minimize performance losses and instability issues.

References

NREL Best Research-Cell Efficiency Chart. https://www.nrel.gov/pv/cell-efficiency.html

Han TH, Tan S, Xue J, Meng L, Lee JW, Yang Y. Interface and Defect Engineering for Metal Halide Perovskite Optoelectronic Devices. Advanced Materials. 2019;31(47). doi:10.1002/adma.201803515

Armenise V, Colella S, Milella A, Palumbo F, Fracassi F, Listorti A. Plasma-Deposited Fluorocarbon Coatings on Methylammonium Lead Iodide Perovskite Films. Energies (Basel). 2022;15(13):4512. doi:10.3390/en15134512

Andrea Listorti, Sara Covella, Alberto Perrotta, et al. A study on plasma-assisted modifications of Methylammonium Lead Iodide Perovskite surfaces for photovoltaic applications.

Xiao X, Bao C, Fang Y, et al. Argon Plasma Treatment to Tune Perovskite Surface Composition for High Efficiency Solar Cells and Fast Photodetectors. Advanced Materials. 2018;30(9):1-7. doi:10.1002/adma.201705176

Figure 1