Structural and Electronic Impact of an Asymmetric Organic Ligand in Diammonium Lead Iodide Perovskites

Abstract

Reduced dimensionality forms of perovskites with alternating layers of organic ligands are a promising class of materials for achieving stable perovskite solar cells. Most work until now has focused on phases utilizing two ammonium terminated ligands per formula unit. However, phases utilizing a single diammonium ligand per formula unit are advantageous in that they can potentially have a thinner insulating organic layer between Pb‐halide layers, yet the structural effects on their optoelectronic properties are not yet well understood. In this study two organic ligands, butane 1,4‐diammonium (BDA) and N,N‐dimethylpropane diammonium (DMPD), are investigated as spacers in n = 1, 2D perovskites. Using ultraviolet and inverse photoelectron spectroscopies, BDAPbI4 is shown to have a larger transport gap by 350 meV and a larger exciton binding energy by 140 meV than DMPDPbI4. Through density functional theory calculations, the cause of this difference is traced to the out‐of‐plane tilting of the Pb‐halide octahedra provoked by the asymmetric ligand in DMPDPbI4. Parallel channels of nearly straight PbIPb bonds are formed in one direction, leading to enhanced electronic coupling and higher band dispersion in that direction. In BDAPbI4, no such channels exist, resulting in greater electronic confinement and a larger bandgap and exciton binding energy.

Metastable Dion-Jacobson 2D structure enables efficient and stable perovskite solar cells

“…We grew the DMePDAPbI 4 -1 single crystal, which was based on the most stable DMePDA 2+ orientation alignment, from a concentrated hydroiodic acid solution using a slow-crystallization process, as adapted from our previous report (23) and consistent with a previous theoretical predication (24). By contrast, the DMePDAPbI 4 -2 single crystal, which was based on a metastable orientational alignment, was formed from either a fast cooling (22) or antisolvent quenching during singlecrystal growth (25), both of which represent a fast-crystallization process.…”

Interlayer Triplet-Sensitized Luminescence in Layered Two-Dimensional Hybrid Metal-Halide Perovskites

“…Moreover, using alkyl-ammonium tethers of varying length gives control over interlayer separation and can be used to manipulate organic layer morphology. , However, while molecular modifications like these offer opportunities, their impact on the structural distortion of the lead-halide layer is often complex and cannot be neglected . The spacer cation size, shape, and dielectric qualities can exert varied effects on the structural and optoelectronic properties of the resulting perovskite, through steric and electrostatic effects, hydrogen bonding, and van der Waals forces. , For more detailed reviews of the structure–property relationships of A′-site cations in layered 2D perovskites, we refer the reader to recent articles by Mao, Li, Gangadharan, Zhang, and co-workers.…”

Inorganic‐Cation Pseudohalide 2D Cs2Pb(SCN)2Br2 Perovskite Single Crystal

“…c) Photoluminescence decay curve of Cs 2 Pb(SCN) 2 Br 2 single crystal measured by time-resolved PL under excitation at 375 nm and detected at 520 nm with a biexponential fitted line. d) Summary chart of exciton binding energy (meV) versus bandgap (eV) for 2D (BA 2 PbI 4 , [12] Cs 2 PbI 2 Cl 2 , [37] BDAPbI 4 , [42] DMPDPbI 4 , [43] PEA 2 PbBr 4 , [20,43] (Decyl-NH 3 ) 2 PbI 4 , [44,45] HA 2 PbBr 4 , [46] and this work Cs 2 Pb(SCN) 2 Br 2 ), quasi-2D (BA 2 MA n−1 Pb n I 3n+1 (n = 2, 3, 4, and 5), [12] PEA 2 MA n−1 Pb n Br 3n+1 (n = 2, 3, 4, and 5), [22] p-FPEA 2 MA n−1 Pb n Br 3n+1 (n = 2, 3, 4, and 5) [22] ), and 3D (MAPbBr 3 , [46] MAPbI 3 , [47] FAPbBr 3 , [47] FAPbI 3 , [47] CsPbCl 3 , [48] CsPbBr 3 , [48] CsPbI 3 , [48] and CsPbI 2 Br [48] ) perovskites. e) UV-vis absorption and PL spectra of Cs 2 Pb(SCN) 2 Br 2 single crystal.…”