Passivation of Bulk Defects in Halide Perovskites thin Films by Plasma Treatment
Aleš Vlk a, Robert Hlaváč a, Lucie Landová a, Julius Vida b, Tomáš Homola b, Antonín Fejfar a, Martin Ledinský a
a Institute of Physics of the Czech Academy of Sciences, Cukrovarnicka 10, 16200 Prague, Czech Republic.
b Institute of Physics of the Czech Academy of Sciences, Cukrovarnicka 10, 16200 Prague, Czech Republic.
Oral, Aleš Vlk, presentation 116
Publication date: 6th February 2024

Recombination of electrons and holes at the defect states of perovskite absorber limits the power conversion efficiency of the organic-inorganic halide perovskite solar cells. Recently, with the help of in-situ PL and GIWAXS measurements, we have shown that the defects are formed mainly at the grain boundaries and surface.1,2 Therefore, it is necessary to selectively passivate surface and grain boundaries. It was shown that the removal of thin surface layers using mechanical,3 or laser4 polishing may improve the performance of perovskite thin films and PCEs.

In our work, we performed an initial study examining the effect of the DCSBD (the diffuse coplanar surface barrier discharge) plasma on perovskite thin films. The sample was placed in the vicinity of the plasma and exposed to the plasma for different duration. Using in-situ photoluminescence (PL) spectroscopy, we found that the exposure of perovskite surface to plasma in nitrogen atmosphere causes the removal of oxygen from perovskite film. We found that, at first, the PL intensity decreased significantly, which is caused by surface defects created by exposure to plasma. However,  after this abrupt change, the plasma lines of singly ionized oxygen appear in the spectrum of the plasma, and the PL intensity increases until the oxygen is completely removed. This means that the removal of oxygen has a positive impact on defect densities in perovskite film. However, when completely removed, further exposure to plasma has only a negative impact.

We believe this method could be an intermediate step before the deposition of a passivation layer on the perovskite. Additionally, the DCSBD plasma treatment is already used in different industrial applications and thus it is ready for use in large production lines.

We acknowledge the use of the CzechNanoLab research infrastructure (LM2023051) and the CEPLANT research infrastructure (LM2023039) supported by the MEYS and project number 9F23003 supported by the MEYS. Furthermore, we acknowledge the support of Czech Science Foundation Project No. 24-11652S.

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