  Perovskite solar cells (PSCs) with superior performance have been recognized
as a potential candidate in photovoltaic technologies. However, the defects in
active perovskite layer induce non-radiative recombination which restricts the
performance and stability of the PSCs. The construction of thiophene-based 2D
structure is one of the significant approaches for surface passivation of
hybrid PSCs that may combine the benefits of the stability of 2D perovskite
with the high performance of 3D perovskite. Here, a sulfur-rich spacer cation
2-thiopheneethylamine iodide (TEAI) is synthesized as a passivation agent for
the construction of three-dimensional/two-dimensional (3D/2D) perovskite
bilayer structure. TEAI-treated PSCs possess a much higher efficiency (20.06%)
compared to the 3D perovskite (MAFAPbI3) devices (17.42%). Time-resolved
photoluminescence (TRPL) and femtosecond transient absorption (TA) spectroscopy
are employed to investigate the effect of surface passivation on the charge
carrier dynamics of the 3D perovskite. Additionally, the stability test of
TEAI-treated perovskite devices reveals significant improvement in humid (RH ~
56%) and thermal stability as the sulfur-based 2D (TEA)2PbI4 material
self-assembles on the 3D surface making the perovskite surface hydrophobic. Our
findings provide a reliable approach to improve device stability and
performance successively, paving the way for industrialization of PSCs.
