Computational Design of Two-Dimensional Perovskites with Functional Organic Cations

Abstract

Two-dimensional (2D) halide perovskites are a class of materials in which 2D layers of perovskite are separated by large organic cations. Conventionally, the 2D perovskites incorporate organic cations as spacers, but these organic cations also offer a route to introduce specific functionality in the material. In this work, we demonstrate, by density functional theory calculations, that the introduction of electron withdrawing and electron donating molecules leads to the formation of localized states, either in the organic or the inorganic part. Furthermore, we show that the energy of the bands located in the organic and inorganic parts can be tuned independently. The organic cation levels can be tuned by changing the electron withdrawing/donating character, whereas the energy levels in the inorganic part can be modified by varying the number of inorganic perovskite layers. This opens a new window for the design of 2D perovskites with properties tuned for specific applications.

Guanine‐Stabilized Formamidinium Lead Iodide Perovskites

“…This finding corroborates the calculated electronic properties of the layered G 2 PbI 4 structure (for details, see the Supporting Information, Section S3.5 and Figures S19–S20), which suggest that the conduction band of the low‐dimensional structure is delocalized within the spacer layer. This has been previously observed for a very few cases of low‐dimensional perovskite structures based on functional organic spacers that can serve as a pathway for charge transport, facilitating charge extraction . Moreover, the calculated hole effective masses along the three principal axes reveal reduced hole effective masses for in‐plane directions coinciding with the π‐stacking of the guanine moieties, suggesting a possible pathway for hole transport.…”

Overcoming the exciton binding energy in two-dimensional perovskite nanoplatelets by attachment of conjugated organic chromophores

“…There are, however, endless possibilities to engineer the electronic structure of 2D hybrid perovskites by introduction of functional organic molecules, for instance strong electron donors or acceptors. As we have shown in a recent theoretical study 15 , such donor or acceptor molecules can directly contribute to the electronic bands. This could result in enhanced charge separation, compared to current 2D perovskites where the organic cation merely acts as a non-functional dielectric spacer-layer, leading to a high exciton binding energy (ranging from~190-400 meV for pure 2D, down to~80 meV for quasi-2D system with four inorganic layers between the organic cations [16][17][18][19] ), and hence inefficient optical generation of charges.…”

2D layered perovskite containing functionalised benzothieno-benzothiophene molecules: formation, degradation, optical properties and photoconductivity

“…23 Therefore, potentially higher charge carrier mobilities in the organic layer may be obtained than those achievable in purely organic thin films. 23 The incorporation of BTBT molecules into the organic layer of a 2D layered perovskite was recently suggested in a computational study by Maheshwari et al 24 According to these calculations, the valence band maximum in such a 2D perovskite should be localized in the organic (BTBT) spacer layer, potentially bestowing ''functional'' properties to the organic layer. This motivated us to embark on an experimental study to incorporate such a BTBT derivative into a 2D layered perovskite.…”