Rigid Conjugated Diamine Templates for Stable Dion–Jacobson-Type Two-Dimensional Perovskites

Abstract

Hybrid organic–inorganic perovskites (HOIPs) have garnered widespread interest, yet stability remains a critical issue that limits their further application. Compared to their three-dimensional (3D) counterparts, two-dimensional (2D)-HOIPs exhibit improved stability. 2D-HOIPs are also appealing because their structural and optical properties can be tuned according to the choice of organic ligand, with monovalent or divalent ligands forming Ruddlesden–Popper (RP) or Dion–Jacobson (DJ)-type 2D perovskites, respectively. Unlike RP-type 2D perovskites, DJ-type 2D perovskites do not contain a van der Waals gap between the 2D layers, leading to improved stability. However, bifunctional organic ligands currently used to develop DJ-type 2D perovskites are limited to commercially available aliphatic and single-ring aromatic ammonium cations. Large conjugated organic ligands are in demand for their semiconducting properties and their potential to improve materials stability further. In this manuscript, we report the design and synthesis of a new set of larger conjugated diamine ligands and their incorporation into DJ-type 2D perovskites. Compared with analogous RP-type 2D perovskites, DJ 2D perovskites reported here show blue-shifted, narrower emissions and significantly improved stability. By changing the structure of rings (benzene vs thiophene) and substituents, we develop structure–property relationships, finding that fluorine substitution enhances crystallinity. Single-crystal structure analysis and density functional theory calculations indicate that these changes are due to strong electrostatic interactions between the organic templates and inorganic layers as well as the rigid backbone and strong π–π interaction between the organic ligands themselves. These results illustrate that targeted engineering of the diamine ligands can enhance the stability of DJ-type 2D perovskites.

Two‐Dimensional Perovskites with Tunable Room‐Temperature Phosphorescence

“…It can be seen that the enhanced octahedra distortion leads to wider bandgaps, consistent with a previous experimental study. [ 52 ] Furthermore, the thermodynamic stability of four candidates is evaluated by ab initio molecular dynamics (AIMD) simulations. The total energies oscillate within a small range in a AIMD simulation time of 5 ps (Figure 5c).…”

Noncrystalline Hybrid Lead Halides with Liquid-Polymer Characteristics

“…For molecular crystals, their formation requires effective molecular packing. Likewise, for HLH crystals with a bulky organic cation, an effective molecular packing of the cation is also required. − In contrast, branched D230 molecules lack this structural requirement. Even though D230 molecules can be introduced into HLHs, they are unable to stack between Pb–Cl frameworks as effectively as other common organic cations.…”

“…Also, in HLH crystals, both organic molecules and lead halide inorganic frameworks are arranged in an orderly manner. Therefore, when it comes to HLHs with a bulky organic molecule, an effective molecular packing is required to reach a crystalline state. − Conversely, most polymers lack structures supporting an effective molecular packing . Crystallization in polymeric materials is much restricted due to many factors such as structural regularity and chain flexibility .…”

Strategies to Improve the Stability of Perovskite Light-Emitting Diodes: Progress and Perspective

“…Similarly, several other organic ligands have been proposed for producing stable 2D DJ MHPs, such as asymmetric N,N-dimethyl-1,3-propanediamine (DPDA) and conjugated 2-fluoro-[1,1′-biphenyl]-4,4′-diyl)-dimethanaminium (FPP). 62,63 Furthermore, those ligand engineering methods intended for optimized 2D phase distribution as presented in Defect Suppression of MHPs were also proved to be favorable for enhancing the EL stability of 2D/quasi 2D PeLEDs.…”

“…Compared with commonly used PEABr, the stronger binding force between P-PDABr 2 and [PbBr 6 ] 4– octahedrons led to stable low-dimensional domains, thereby improving the spectral stability of deep-blue PeLEDs. Similarly, several other organic ligands have been proposed for producing stable 2D DJ MHPs, such as asymmetric N , N -dimethyl-1,3-propanediamine (DPDA) and conjugated 2-fluoro-[1,1′-biphenyl]-4,4′-diyl)-dimethanaminium (FPP). , Furthermore, those ligand engineering methods intended for optimized 2D phase distribution as presented in Defect Suppression of MHPs were also proved to be favorable for enhancing the EL stability of 2D/quasi 2D PeLEDs.…”