Perovskite solar cells have undergone significant advancements in recent years, with a strong focus on optimizing
perovskite crystallization and surface passivation. One promising avenue for improving the light absorption and
electrical properties of perovskite layers is the incorporation of plasmonic nanoparticles. In this study, we investigate
the effects of TiN nanoparticles on the structural, morphological, electrical, and optical properties of
Cs0.05(FAPbI3)0.83(MAPbBr3)0.12 (referred to as CsFAMA) perovskite.

Prior to conducting experimental measurements, we performed optical finite-difference time-domain (FDTD)
simulations to assess the anticipated impact of embedding TiN nanoparticles into CsFAMA on the optical absorptance
spectra. Our simulations revealed moderate increases in absorptance within the visible range, accompanied by notable
enhancements in the near-infrared region. Subsequent real UV-Vis-NIR measurements closely aligned with the
simulation results, with one exception: the overall reflectance of TiN-containing perovskite films exhibited a decrease.
We attribute this phenomenon to the higher crystallinity and larger size of CsFAMA grains, as confirmed through X-
ray diffraction (XRD) and scanning electron microscopy (SEM), respectively.

To gain further insights into the structural and morphological changes resulting from the presence of TiN nanoparticles,
we conducted an aging study on as-deposited, unannealed CsFAMA films for a duration of 3 hours, followed by XRD
measurements on the aged films. Our observations and XRD results indicate that as the content of TiN nanoparticles
increases, the re-dissolution of CsFAMA becomes more pronounced, suggesting a larger quantity of trapped solvents
within the perovskite film. Consequently, the apparent increase in grain size can be attributed to the ability of TiN
nanoparticles to adsorb trace amounts of dimethyl sulfoxide (DMSO), leading to a less rigid perovskite film that
crystallizes at a slower rate, thus facilitating the growth of larger crystals. These findings are in line with TGA and
DSC measurements results.

X-ray photoelectron spectroscopy (XPS) analysis revealed the absence of TiN on the perovskite surface, indicating
that the TiN nanoparticles are situated either at the TiO2/CsFAMA interface or within the CsFAMA structure. Finally,
we constructed perovskite solar cells incorporating TiN nanoparticles, resulting in increased efficiency related to an
improvement of all electrical properties of solar cell (Jsc, Voc and FF). Our measurements of the incident photon-to-
electron conversion efficiency (IPCE) demonstrated enhanced performance arising from both the larger size of
perovskite grains and electron transfer from plasmonic nanoparticles at resonance wavelengths. Larger size of grains
led to reduction in the recombination, as evident from PL results. As a result, the incorporation of TiN led to an
increase in PCE from 19.0% to 21.4%.

In summary, the presence of TiN nanoparticles significantly influences the structural, morphological, electrical, and
optical properties of CsFAMA perovskite. The incorporation of TiN nanoparticles leads to improved absorptance,
enhanced crystallinity, larger grain sizes, and increased efficiency of perovskite solar cells. These findings contribute
to the ongoing efforts to advance the development of high-performance perovskite-based photovoltaic devices.

Keywords: Plasmonic nanoparticles, TiN for CsFAMA perovskite, refractory metals plasmonic nanoparticles,
controlled CsFAMA crystallization.