Structure-Dependent (Non)Linear Optical Excitons in Primary Cyclic Ammonium (C_nH_2n–1NH₂;n= 3–8)-Based Inorganic–Organic Hybrid Semiconductor Series

Abstract

This work reports the synthesis, structural, linear, and nonlinear optical investigations into low-dimensional naturally selfassembled inorganic−organic (IO) hybrid systems based on (C n H 2n−1 NH 3 ) + (n = 3−8) cyclic moieties. The steric effects of cyclic ring sizes convert the IO hybrids from two-dimensional (2D) layered structures to 1D crystal packing. The crystal packing of this class of IO hybrid compounds of cyclic sizes from n = 3 to 6 shows a perfect 2D layered structural arrangement having a crystal structure (R−NH 3 ) 2 PbI 4 . On the contrary, n = 7 hybrid shows a 1D layered structural arrangement, but the adjacent chains are disconnected along the "c"-axis, resulting into (R−NH 3 ) 3 PbI 5 . Moreover, for n = 8 hybrids, the inorganic network structure is infinitely extended along the "a"-axis having (R−NH 3 )PbI 3 1D crystal structure. These structural changes may lead to defect states, which is verified by density functional theory (DFT) calculations. The linear and nonlinear optical probing of room-temperature optical excitons demonstrate the photoluminescence and absorption feature variation from 2D layered crystal packing (n = 3−6) to quasi-1D structures (n = 7, 8). A systematic correlation of one-photon (1PA)-and two-photon (2PA)-excited exciton photoluminescence (PL) features with a cyclic size is discussed and presented. While one-photon absorption-induced photoluminescence (1PA-PL) provides information about strong exciton emission from the top few perfectly aligned layers, twophoton excitation probes the deeper depths. This shows red-shifted PL (2PA-PL) from the structurally distorted crystal packing within the sample and traces of defect-induced emission. The DFT study shows that the I-vacancy defect creates the states at conduction band minimum (CBm), which leads to a sudden reduction in the band gap for n = 7 and 8. The systematic optical probing studies to determine the structural deviations in IO hybrid semiconductors will provide a new platform for advanced photonics and optoelectronic devices.

Thermochromic Phase Transitions of Long Odd-Chained Inorganic–Organic Layered Perovskite-Type Hybrids [(CnH2n+1NH3)2PbI4], n = 11, 13, and 15

“…Hybrids that have long-chain alkylammonium chains of the general formula (C n H 2 n +1 NH 3 ) 2 MX 4 (abbreviated C n PbX) are especially prone to conformational changes within the chains and positional changes relative to the inorganic layers. In the past, the hybrids have also been known as natural multiple quantum well structures, − which lead to excitonic and optoelectronic properties, − especially the even-chained hybrids C n PbX (X = Cl, Br, or I), with n = 4, 6, 8, 10, and 12. − …”

Sn/Ge Substitution in ((CnH2n–1NH3)2PbI4; n = 3–6): An Emerging 2D Layered Hybrid Perovskites with Enhanced Optoelectronic Properties

“…There are changes in tilting of PbI 6 octahedra within layers and packing of ammonium cations between layers of these compounds, but the overall structure remains the same, i.e., 2D layered perovskite crystal structure (see Figure ). These cyclic inorganic–organic hybrid compounds have been synthesized experimentally and show a decrement in electronic bandgap value from n = 3 to n = 6, an intense narrow exciton emission, and a strong room-temperature photoluminescence. , However, these compounds have some drawbacks, such as a wide bandgap and the presence of toxic element Pb. Therefore, to overcome these issues, which are not good for solar cells, we have studied the effect of Ge/Sn substitution and/or Pb-□ using hybrid DFT.…”

“…Therefore, there is justified interest to search for a stable and efficient 2D (layered) perovskite material with good optical absorption. Incidentally, we have studied and experimentally synthesized the primary cyclic ammonium-based (C n H 2 n –1 NH 3 ; n = 3–6) inorganic–organic hybrid semiconductor series . However, theoretically, this system ((C n H 2 n –1 NH 3 ) 2 PbI 4 ; n = 3–6) is rather unexplored and requires further attention to get more atomistic insights and electronic structures.…”

Sn/Ge substitution in ((C$_\textrm{n}$H$_{2\textrm{n}-1}$NH$_3$)$_2$PbI$_4$; n=3): An emerging 2D layered hybrid perovskites with enhanced optoelectronic properties$^†$

“…21 These cyclic inorganic-organic hybrid compounds have been synthesized experimentally, and show a decrement in electronic bandgap value from n = 3 to 6, an intense narrow exciton emission, and a strong roomtemperature photoluminescence. 36,45 However, these compounds have some drawbacks, such as wide bandgap and presence of toxic element Pb. Therefore, to overcome these issues, which are not good for solar cell, we have studied the effect of Ge/Sn substitution and/or Pb-using hybrid DFT.…”

“…Therefore, there is justified interest to search for a stable and efficient 2D (layered) perovskite material with good optical absorption. Incidentally, we have studied and experimentally synthesized the primary cyclic ammonium-based (C n H 2n-1 NH 3 ; n = 3−6) inorganic-organic hybrid semiconductor series 36 . However, theoretically this system ((C n H 2n−1 NH 3 ) 2 PbI 4 ; n=3-6) is rather unexplored and requires further attention to get more atomistic insights and electronic structures.…”