The
commonly employed formamidinium (FA)-containing perovskite
solar cells (PSCs) exhibit a severe phase instability problem, thereby
limiting their commercial applications. Here, both phase stability
and energy efficiency of FA-based PSCs were improved by treating the
perovskite surface with pyrrolidinium hydroiodide (PyI) salts, resulting
in a 1D perovskite structure (PyPbI3), stacked on the original
3D perovskite. By employing in situ XRD measurements, we revealed
that the temperature-dependent phase transition activation barrier
was enhanced after forming the 1D/3D structure, resulting in a prolonged
transition time by 30–40-fold. From the first-principle calculations,
we found the thermodynamic energy difference between two phases reduced
from −0.16 to −0.04 eV after the stacking of 1D PyPbI3, offering additional lifetime improvement. Moreover, the
champion 1D/3D bilayer PSC exhibits a boosted power conversion efficiency
of 19.62%, versus 18.21% of the control. Such 1D/3D bilayer structure
may be employed in PSCs to enhance their phase stability and photovoltaic
performance.
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