Organic
spacers play a crucial role in two-/three-dimensional (2D/3D)
hybrid perovskite-based solar cells that integrate the advantages
of the stability of 2D perovskites and the high efficiency of 3D perovskites.
However, improving the stability of the device without compromising
the high photovoltaic efficiency in 2D/3D perovskite solar cells using
large organic cations in 2D perovskite is a challenge. Herein, we
synthesized 2-thiopheneethylammonium iodide (TEAI) and found that
TEAI can perform as a spacer for 2D/3D hybrid perovskites. TEAI with
a bulky aromatic spacer in 2D/3D hybrid perovskites can effectively
induce crystalline growth and orientation, leading to a longer carrier
lifetime, higher carrier mobility, fewer surface, and grain boundary
defects. The inclusion of TEAI also improves surface hydrophobicity.
The 2D/3D hybrid perovskite device based on TEAI achieved the highest
efficiency of 18.75% compared with the 16.83% efficiency of the 3D
perovskite device. After aging for 1000 h in an ambient atmosphere,
the unpackaged 2D/3D hybrid perovskite solar cells maintained approximately
82% of their initial efficiency, whereas that of the controlled devices
decreased to approximately 47% of their original performance. These
results suggest that TEAI can be used as an organic spacer for the
preparation of high-efficiency and high-stability 2D/3D perovskite
solar cells.
Perovskite crystal quality plays an important role in perovskite solar cells, given that multiple grain boundaries and trap states in the perovskite films hamper further enhancement of solar cell efficiency. Using the solution method to prepare perovskite films with large grains and high coverage requires further improvements. Herein, we introduce Lewis base urea as an additive into the precursor of perovskite to control the crystallization dynamics, allowing for large-grain crystal growth. As a result, MAPbI3 films with urea as an additive are well crystallized with large crystal grains of sizes >3 μm. The large-grain perovskite is found to simultaneously improve the power-conversion efficiency (PCE) and device stability. With an optimal urea additive of 20 mol%, the PCE is significantly increased from 15.47% for the reference MAPbI3 solar cell to 18.53% for the device with MAPbI3 with urea as an additive. Finally, the optimized device demonstrates excellent stability and maintains 80% of the initial PCE after 60 days.
Nickel chloride hexahydrate (NiCl2·6H2O) was introduced into the SnO2 ETL, which significantly increased open-circuit voltage (VOC) and power conversion efficiency (PCE)
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