Narrow-Bandgap Mixed Lead/Tin-Based 2D Dion–Jacobson Perovskites Boost the Performance of Solar Cells

The advent of the
two-dimensional (2D) family of halide perovskites
and their demonstration in 2D/three-dimensional (3D) hierarchical
film structures broke new ground toward high device performance and
good stability. The 2D Dion–Jacobson (DJ) phase halide perovskites
are especially attractive in solar cells because of their superior
charge transport properties. Here, we report on 2D DJ phase perovskites
using a 3-(amino­methyl)­piperid­inium (3AMP) organic
spacer for the fabrication of mixed Pb/Sn-based perovskites, exhibiting
a narrow bandgap of 1.27 eV and a long carrier lifetime of 657.7 ns.
Consequently, solar cells employing mixed 2D DJ 3AMP-based and 3D
MA0.5FA0.5Pb0.5Sn0.5I3 (MA = methyl­ammonium, FA = formamid­inium) perovskite
composites as light absorbers achieve enhanced efficiency and stability,
giving a power conversion efficiency of 20.09% with a high open-circuit
voltage of 0.88 V, a fill factor of 79.74%, and a short-circuit current
density of 28.63 mA cm–2. The results provide an
effective strategy to improve the performance of single-junction narrow-bandgap
solar cells and, potentially, to give a highly efficient alternative
to bottom solar cells in tandem devices.