Effects of Cl and F Substitution in Phenylethylammonium Spacer Cations on Stability, Structure, and Optical Properties of 2D–3D Ruddlesden–Popper Perovskite Layers

Abstract

Recent experiments on chemical tuning of spacer cations (phenylethylammonium: PEA) with electronegative entities such as Cl or F in 2D–3D Ruddlesden–Popper (RP) perovskite layers show simultaneous improvement in their device performance and stability. In order to understand the role of such substitution on the properties and stability of 2D and 2D−3D layers of PEA2PbI4 with engineered spacer cations, here we present results of state-of-the-art ab initio calculations. It is found that Cl and F substitution in spacer cations does not affect much the inorganic framework but increases the stability of the layered compounds. This enhancement in stability is attributed to strong van der Waals interactions particularly in the case of Cl substitution. Moreover, a rotation of the phenyl ring does not significantly affect the electronic and optical properties of the 2D–3D RP perovskite layers. However, the chemical tuning of PEA spacer cations results in a moderate blue shift in the optical absorption spectra. Further study on F- and Cl-substituted PEA2PbBr4 layers show their better stability than in the case of iodides and the possibility of applications in blue light-emitting diodes. Our results are in very good agreement with the available experimental findings and pave the way toward a better understanding of the more stable RP perovskite layers for photovoltaic and optoelectronic applications.

Revealing the Transient Formation Dynamics and Optoelectronic Properties of 2D Ruddlesden‐Popper Phases on 3D Perovskites

“…[28] This versatility, however, makes it difficult to draw general conclusions regarding the formation and functioning of the 2D/3D interfaces. Several properties of these bulky cations and their salts influence the 2D film formation, as well as incorporation into 2D/3D structures and, therefore, device performance: for instance, the length of the alkyl chain of the bulky molecule, [18,29,30] the choice of its halide anion, [16,31,32] and the choice of its aromatic backbones and their substituted analogues. [11,[33][34][35] Furthermore, there is an ongoing debate about the optimal way of incorporating the bulky molecules into the 3D-pvsk film.…”

Surface Regulation through Dipolar Molecule Boosting the Efficiency of Mixed 2D/3D Perovskite Solar Cell to 24%

“…[ 26,28 ] Moreover, the fluorinated terminal group with hydrophobic property can protect perovskite from the corrosion of water molecules, which is speculated to improve the device stability. [ 29 ] The increased hydrophobicity of TFPhFACl treated perovskite can be verified by measuring the water contact angle, as shown in Figure S1 (Supporting Information). With TFPhFACl treatment, the water contact angle increases from 45.09° to 54.32°, indicating the enhanced water‐resistivity, which is beneficial for the device stability.…”

Surface modification strategy based on molecular engineering of an organic cation toward spectrally stable deep-blue emission perovskites

“…The results of density functional theory calculations show that the overall charge number of the -NH 3 + functional group in 2N is +0.535, which in 4N is +0.578, indicating that the increasing of electron withdrawing groups -NH 3 + can make -NH 3 + in the organic ligand show a stronger positive charge. 26 The -NH 3 + functional group with stronger positive charge can achieve a better surface modification effect on halogen ions, which endows 4N with a better modification ability. The radiative transition rate (k r ) and non-radiative transition rate (k nr ) of CsPbBr 3Àx Cl x were calculated with PLQY and t avg .…”