Oxygen-Containing Diamine Cations Enable Highly Efficient and Stable 2D Dion-Jacobson Perovskite Solar Cells

Two-dimensional
(2D) Dion–Jacobson (DJ) perovskites have
been extensively investigated in perovskite solar cells (PSCs) owing
to their superior stability and structural diversity. However, the
efficiency is still limited by dielectric confinement and carrier
localization in the transport process. Here, we introduced a new spacer
cation, namely, 2,2′-oxybis(ethylamine) hydroiodide (OBEAI),
which clearly clarified the fundamental physical properties of constructing
2D DJ perovskites to optimize charge transfer properties for high-performance
2D DJ PSCs. The strong electronegativity of OBEA enhanced the overlap
of charge density in the spacing through its interaction with inorganic
[PbI6]4– layers, promoting charge migration
across confinement layers. In addition, the aggregation of strong
electronegativity of OBEA and metal cations in precursor solutions
enlarged the particle size, which reduced random nucleation sites,
thereby inhibiting the production of low n-value
perovskites (n ≤ 2). Thanks to these merits,
the electrons’ transport of (OBEA)MA4Pb5I16 (MA: methylamine) was greatly promoted, which supported
efficient charge extraction at the device level. The resultant (OBEA)MA4Pb5I16 solar cells delivered a power
conversion efficiency (PCE) of 14.33% and further improved to 18.81%
based on (OBEA)FA4Pb5I16 (FA: formamidine)
with exceptional stability of T90 (preserve
90% of the initial PCE) after 2000 h.