Thick-Layer Lead Iodide Perovskites with Bifunctional Organic Spacers Allylammonium and Iodopropylammonium Exhibiting Trap-State Emission

Abstract

The nature of the organic cation in two-dimensional (2D) hybrid lead iodide perovskites tailors the structural and technological features of the resultant material. Herein, we present three new homologous series of (100) lead iodide perovskites with the organic cations allylammonium (AA) containing an unsaturated CC group and iodopropylammonium (IdPA) containing iodine on the organic chain: (AA)2MA n –1Pb n I3n+1 (n = 3–4), [(AA) x (IdPA)1–x ]2MA n –1Pb n I3n+1 (n = 1–4), and (IdPA)2MA n –1Pb n I3n+1 (n = 1–4), as well as their perovskite-related substructures. We report the in situ transformation of AA organic layers into IdPA and the incorporation of these cations simultaneously into the 2D perovskite structure. Single-crystal X-ray diffraction shows that (AA)2MA2Pb3I10 crystallizes in the space group P21/c with a unique inorganic layer offset (0, <1/2), comprising the first example of n = 3 halide perovskite with a monoammonium cation that deviates from the Ruddlesden–Popper (RP) halide structure type. (IdPA)2MA2Pb3I10 and the alloyed [(AA) x (IdPA)1–x ]2MA2Pb3I10 crystallize in the RP structure, both in space group P21/c. The adjacent I···I interlayer distance in (AA)2MA2Pb3I10 is ∼5.6 Å, drawing the [Pb3I10]4– layers closer together among all reported n = 3 RP lead iodides. (AA)2MA2Pb3I10 presents band-edge absorption and photoluminescence (PL) emission at around 2.0 eV that is slightly red-shifted in comparison to (IdPA)2MA2Pb3I10. The band structure calculations suggest that both (AA)2MA2Pb3I10 and (IdPA)2MA2Pb3I10 have in-plane effective masses around 0.04m 0 and 0.08m 0, respectively. IdPA cations have a greater dielectric contribution than AA. The excited-state dynamics investigated by transient absorption (TA) spectroscopy reveal a long-lived (∼100 ps) trap state ensemble with broad-band emission; our evidence suggests that these states appear due to lattice distortions induced by the incorporation of IdPA cations.

Abnormal In-Plane Thermomechanical Behavior of Two-Dimensional Hybrid Organic–Inorganic Perovskites

“…It is thus crucial to understand the mechanical properties and their relationship to the internal chemistry/structure of the materials. The intrinsic structure–property relationship of 2D HOIPs regarding their elastic behavior has been widely explored by nanoindentation, − atomic force microscopy (AFM), , the wrinkling instability method, and transient reflection measurements . Unlike in 3D HOIPs, the organic component (particularly the organic spacer molecules) and the interfaces between the organic layers play essential roles in determining the mechanical behavior of 2D HOIPs. ,,, …”

Determining the Role of the Molecular Weight of Poly(Ethylene Glycol) Additives in Perovskite Photodetectors

“…These results indicate that the grain size can be tailored by changing the molecular weight of the PEG additive, which is attributable to the impact of the PEG additive on the crystallization kinetics of the perovskite film . PEG is often considered a Lewis base due to the ether group C–O–C with lone-pair electrons and which allows the formation of Lewis acid–base interactions with the positively charged defects such as undercoordinated Pb 2+ in the CsPbI 2 Br perovskite, while Pb 2+ is regarded as a Lewis acid since Pb­(II) halides prefer to accept iodide anions to form iodo-plumbate anions such as [Pb 3 I 10 ] 4– and [Pb 5 I 16 ] 6– . − The formed Lewis acid–base interaction between PEG and Pb 2+ allows us to tune the crystallization of the CsPbI 2 Br perovskites and further impacts the morphology and optoelectronic properties in perovskite films by changing the PEG molecular weight in the following aspects . First of all, the increase in the PEG molecular weight from 6k to 10k results in an increase in the nucleation energy barrier to reduce the quantity of the perovskite crystal nucleus .…”

Design rules for obtaining narrow luminescence from semiconductors made in solution

“…[408][409][410][411] On the other hand, the organic "spacer" cation influences indirectly the structure of the inorganic framework through its resultant non-covalent templating and through properties such as crystallinity, solubility, mechanical behavior, and thermochemical stability. [412][413][414][415][416][417][418] The superior environmental stability of 2D hybrid lead iodide perovskites and their inherent structural flexibility has rendered them attractive alternatives to 3D perovskites for the fabrication of environmentally robust optoelectronic devices. 68,366,417,[419][420][421][422][423][424][425][426][427] Photophysical studies have mainly been focused on lead halide perovskites due to their strong, excitonic PL emission.…”