Perovskite
solar cells (PSCs) that incorporate a two-dimensional/three-dimensional
(2D/3D) perovskite layer demonstrate enhanced stability compared to
that of their purely three-dimensional counterparts. This improved
stability can be attributed to the superior chemical stability of
the 2D perovskite layer. However, the poor electrical properties of
the 2D perovskite layer also limit further improvement of device performance.
Moreover, as the most effective hole transport layer (HTL) in 2D/3D PSCs, lithium bis(trifluoromethylsulfonyl)imide (Li-TFSI)-doped
2,2′,7,7′-tetrakis(N,N-di(4-methoxyphenyl)amino)-9,9-spirobifluorene (spiro-OMeTAD) usually
needs prolonged exposure to air to improve its conductivity, which
to some extent increases the risk of water/oxygen infiltrating into
the perovskite layer, leading to the degradation of the perovskite
active layer. Herein, we developed a multifunctional dopant, tin oxysulfide
(SnSO) in the spiro-OMeTAD layer to improve the efficiency and stability
simultaneously. On one hand, SnSO accelerates the oxidation of the
spiro-OMeTAD film and significantly improves its conductivity. On
the other hand, strong interaction among the SnSO with 2D perovskite
makes up for the poor conductivity of 2D perovskite and passivates
perovskite defects, which also creates an interface built-in electric
field to improve hole transport efficiency and reduce charge recombination
at the 2D/HTL interface. Furthermore, the doping of SnSO makes the
energy level arrangement at the 2D/3D interface more favorable for
carrier transfer. Finally, after optimizing the doping concentration
of SnSO, the target device achieved a high photoelectric conversion
efficiency (PCE) of 24.5%. Simultaneously, the device’s stability
increased dramatically under various testing conditions.