Structural and Electronic Properties of Two-Dimensional Organic–inorganic Halide Perovskites and their Stability against Moisture

Abstract

Organic–inorganic halide perovskites have attracted increasing interest for solar-energy harvesting because of the simple fabrication process, high efficiency, and low cost. In this work, we systematically investigate the structural and electronic properties, and stability of two-dimensional (2D) hybrid organic–inorganic perovskites (HOIPs) based on density-functional-theory calculations. We explore a general rule to predict the bandgap of the 2D HOIP: its bandgap decreases as the thickness increases and the size of metal atom decreases as well as that of the halide atom increases. We find that effective mass of hole increases as the thickness of 2D HOIP increases. Importantly, the 2D HOIPs exhibit high stability on the resistance of water and oxygen than bulk HOIPs due to high positive adsorption energy. Our results confirm that the 2D HOIPs may be excellent alternatives to the unstable bulk HOIPs in solar energy harvesting with improved performance due to suitable bandgap, small carrier effective mass, and high resistance to water and oxygen molecules.

Theoretical Progress on the Relationship between the Structures and Properties of Perovskite Solar Cells

“…The structural flexibility and tunability as well as the significant quantum confinement effects of the low dimension perovskites provide a rich and fertile "playground" for the prepa-ration of interesting crystal structures with various properties predicted by calculations, such as tunable bandgap, Rashba band splitting, and high stability against moisture, oxygen, and heat. [97][98][99][100][101] As shown in Figure 2, the 2D (C 4 H 9 NH 3 ) 2 PbX 4 (X = Cl, Br, and I) hybrid perovskites showed the layer dependent properties. [102] For example, the effect mass of hole m h * increases in proportion to the decreased layer thickness, the absorption peaks redshift from 502 nm for the single layer to 519 nm for the sextuple layer, and converge at 522 nm for bulk (C 4 H 9 NH 3 ) 2 PbI 4 .…”

Mixed Two-Dimensional Organic-Inorganic Halide Perovskites for Highly Efficient and Stable Photovoltaic Application

“…The 2D-HOIPs with different phases (tetragonal and orthorhombic) can be obtained due to the orientation of C–N bonds with the MA cations. Our previous study demonstrated that the 2D tetragonal phase with the parallel (TETP) structure of the C-N bonds shows the highest efficiency for solar-to-power conversion [40]. Therefore, in this study, we focus on the TETP structures with three inorganic sheets ( n = 3) of 2D-HOIPs, including SnI-2D-HOIPs, PbI-2D-HOIPs, SnBr-2D-HOIPs and PbBr-2D-HOIPs.…”

“…We focus on the SnI-2D-HOIPs mixed with different composition ratios of the Cs, Rb, Ge and Pb atoms. The energy for molecule adsorption (E a ) can be calculated as follows [40]:Ea=Em/S−ES−Em where E m/S , E S , and E m are the energies of the mixed 2D-HOIP with molecule, the 2D-HOIPs, and the molecule, respectively. If E a is negative, the slab surface is an easy to adsorb molecule, while the surface is repulsive if the energy is positive.…”

“…Despite noticeable and extremely fast progress in the improved stability, almost all of the research on compositional engineering were focused on the 3D-HOIP materials, while for the 2D-HOIPs that show controllable bandgap, multi-functional properties, and high stability [40], more study is still required. However, the low PCE is their bottleneck.…”

Halide perovskite photocatalysis: progress and perspectives

“…Furthermore, after electrons and holes are generated, they can recombine quickly, which lowers the performance of catalysts. 17 Various strategies have been developed to tackle these challenges. Z-scheme photocatalytic systems that used two connecting photocatalysts were a potential approach for improving photocatalytic activity, and their photocatalytic activity was superior to that of single-component photocatalysts.…”