Effects of Organic Moieties on Luminescence Properties of Organic–Inorganic Layered Perovskite-Type Compounds

Abstract

The effects of organic moieties on the luminescence properties of organic−inorganic layered perovskite-type compounds were investigated. Three single crystals were fabricated, namely, (C 4 H 9 NH 3 ) 2 PbBr 4 {C4}, (C 6 H 5 CH 2 NH 3 ) 2 PbBr 4 {Ben}, and (C 6 H 5 C 2 H 4 NH 3 ) 2 PbBr 4 {Phe}. Among the single crystals, the exciton emission of Phe showed the highest quantum efficiencies. The quantum efficiencies of C4 and Ben only were 0.02 and 0.17 times that of Phe, respectively. The radiative and nonradiative decay rates were calculated from the quantum efficiencies and luminescence lifetimes. The relative values of the quantum efficiencies were in accordance with the values of the radiative decay rates. The results indicate that the luminescence properties of the organic−inorganic hybrid compounds may be governed by the excitonic properties of the inorganic layer and not by the concentration of any structural defects. Focusing on the geometry of the inorganic layers, the Pb−Br−Pb bond angles between the adjoining PbBr 6 2− octahedra of each compound were 150°(Ben), 152°(Phe), and 155°(C4). In addition, only Phe showed structural distortion inside the PbBr 6 2− octahedron with Br−Pb−Br bond angles of 171°. The increase in the radiative decay rate can be attributed to the increase in the reduced mass of the excitons from these structural distortions that lead to a decrease in the Bohr radius of the excitons. The results indicate that the luminescence properties of the organic−inorganic hybrid compounds are governed by the structural geometry of the inorganic layer.

Toward Fluorinated Spacers for MAPI-Derived Hybrid Perovskites: Synthesis, Characterization, and Phase Transitions of (FC2H4NH3)2PbCl4

“…27−29 As can be seen in Figure 5a, a clear separation between the absorption band edge and the excitonic peak for (FC 2 H 4 NH 3 ) 2 PbCl 4 cannot be observed, but there is an overlap of a peak at 328 nm and the band edge. Such a close occurrence of an excitonic absorption peak and the band edge has already been reported for other organic−inorganic layered perovskite compounds 30 and can be explained by the fact that the optical properties strongly depend on the organic moiety. Possible effects of the organic layer on excited states within the inorganic layer include a change of the exciton binding energy depending on the organic layer's dielectric constant, a potential energy transfer into the organic layer, 31 and structural distortions of the inorganic layer imposed by the organic layer.…”

“…Possible effects of the organic layer on excited states within the inorganic layer include a change of the exciton binding energy depending on the organic layer's dielectric constant, a potential energy transfer into the organic layer, 31 and structural distortions of the inorganic layer imposed by the organic layer. 30,32,33 Con sequently, differences in optical properties for different organic−inorganic layered perovskite compounds can be expected. While for excitation above the bandgap, no significant photoluminescence can be detected ( Figure S5a); excitation into the sub bandgap absorption feature between 350 and 400 nm leads to a strong and broad photoluminescence (PL) spectrum (Figure 5a).…”

Color-Pure Violet-Light-Emitting Diodes Based on Layered Lead Halide Perovskite Nanoplates

“…This 2D material naturally forms repeating quantum well structures, as schematically shown in Figure 1B, that tightly confine excitons within the inorganic layers, leading to high exciton binding energies (350 -480 meV) 37 and strong, stable PL at room temperature. 36 Narrow, violet PL was previously reported for (PEA)2PbBr4. 38 The quantum confinement and high excitons binding energies are believed to increase the LED efficiency.…”

“…Layered 2D organolead halide perovskites are described by the general formula (RNH3)2PbX4, where R is an aryl or alkyl substituent and X is a halogen. [31][32][33] Specifically, using 2-phenylethylammonium (C6H5CH2CH2NH3 + , PEA, also called 4 phenethylammonium) as the organic cation yields 2D layered perovskites (PEA)2PbBr4 (crystal structure shown in Figure 1A), 36 in which layers of the inorganic semiconductor (sheets of corner-sharing PbBr6 octahedra) are sandwiched between layers of insulating PEA counter cations. The spacing between inorganic layers is 1.69 nm.…”

Enhanced Environmental Stability of Planar Heterojunction Perovskite Solar Cells Based on Blade‐Coating

“…The best performing reference device shows a PCE of 10.30%, and the detailed photovoltaic properties of the reference perovskite cells are shown in Figure S1 in the Supporting Information. Current densityvoltage ( J -V ) characteristics of perovskite solar cells fabricated with two coating methods in ambient conditions are shown in Figure 2 a, with summarized device performance in Table 1 .Hybrid organic-inorganic halide perovskites have attracted signifi cant attention from both academia and industry due to their unique structural and optoelectronic properties such as high crystallinity, excellent charge carrier mobility, luminescence and energy harvesting characteristics [1][2][3][4][5][6][7][8][9][10][11][12] that led to very rapid progress in perovskite solar cells. [13][14][15][16] However, fabrication of high-performance perovskite solar cells, particularly those based on compact titanium dioxide (TiO 2 ) electron-transporting layers, involves high temperature (≈500 °C) sintering process to increase crystallinity for achieving high charge carrier mobility.…”