Surface Property Tuning of Methylammonium Lead Iodide by Plasma for Use in Planar Perovskite Solar Cells

Abstract

The demand for cheap and green energy as a replacement for fossil fuels has never been greater, and perovskite solar cells (PSCs) are among the leading means of meeting it. The surface properties of metal halide perovskite layers play crucial roles in the performance and durability of such cells. Consequently, a wide range of engineering processes for surface modification of perovskite layers has been investigated and among them is atmospheric pressure plasma (APP). Nevertheless, knowledge of the interaction between plasma and perovskite layers is still far from complete. In this work, CH 3 NH 3 PbI 3 films were subjected to APP generated by a portable plasma source. A detailed understanding of band energy after plasma treatment is crucial to the investigation of the behavior of the perovskite layer. This study demonstrates a remarkable shift in the valence and conduction bands of a perovskite layer after plasma treatment, while band gap energy remains relatively constant. We found that short plasma treatment of perovskite layers resulted in higher performance and stability of PSCs.

Plasma-Deposited Fluorocarbon Coatings on Methylammonium Lead Iodide Perovskite Films

“…In Figure 5, the UV-vis absorption and the PL spectra of pristine and coated MAPbI 3 films are reported. The UV-vis spectra (Figure 5a) all exhibit the same trend with the absorption onset at approximately 780 nm, typical of the MAPbI 3 perovskite [26,41]. This absorption onset remains constant also after the plasma deposition of the perfluorocarbon coating, indicating that the plasma processes have no effect on the bulk perovskite material properties, but they affect just the surface [38].…”

“…On the contrary, samples obtained after the plasma deposition of the fluorocarbon coating on the perovskite carried out for 10 s show only a partial degradation after two weeks of exposure to air, preserving its absorption onset related to the perovskite optoelectronic properties, and exhibit a complete degradation after six weeks of storage in air (Figures 6 and 7c). Furthermore, samples obtained after the plasma deposition of the fluorocarbon coating on the perovskite carried out for 60 s do not show a complete degradation even after eight weeks of exposure to open air (Figure 6), continuing to present the absorption characteristics typical of MAPbI 3 perovskite films (Figure 7d) [26,41].…”

“…Therefore, the possibility to use plasma to tune their surface allowing them to further improve their performances and/or their stability would represent an interesting frontier for scientific research. Some studies on the application of plasma treatment and/or etching on perovskite films have been reported in the literature [33][34][35][36][37][38][39][40][41]. Particularly, Kim et al [33] treated methylammonium lead iodide (MAPbI 3 ) perovskite layers with an H 2 -containing AP plasma for patterning their surface.…”

“…Xiao et al [34] and Li et al [35] employed Ar fed plasmas to modify the surface composition of the MAPbI 3 film. The effects of ambient-air plasma treatment and of an LP O 2 one on perovskite films were examined [36][37][38], and some studies analysed the effects of plasma treatments on the MAPbI 3 coatings directly performed in the nitrogen-filled glove box, necessary for the perovskite deposition [39][40][41].…”

Low‐Temperature and Rapid Deposition of an SnO2 Layer from a Colloidal Nanoparticle Dispersion for Use in Planar Perovskite Solar Cells

“…For plasma treatment, the samples were exposed to atmospheric plasma generated by RPS400 (Roplass s.r.o., Czech Republic) used with diffuse coplanar surface barrier discharge plasma unit capable of generating a plasma of very high‐power density at low gas temperature. The coplanar surface dielectric barrier discharge was already tested for mild treatment of perovskite layers in p‐i‐n PSCs leading to better stability [ 50 ] and rapid low‐temperature fabrication of m‐TiO 2 electron transporting layer in n‐i‐p PSCs. [ 51 ] In this work, the SnO 2 surfaces were exposed to atmospheric argon plasma for 5 min.…”