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Multiexcitonic Broad-Band Emission Enhanced by Resonant Energy Transfer in a New Two-Dimensional Organic−Inorganic Perovskite: (C3H8N6)PbCl4

AUTEURS : O. Medhioub, A. Samet, H. Barkaoui, S. Triki, and Y. Abid

CITATION: J. Phys. Chem. C 2020
DOI: 10.1021/acs.jpcc.0c04768

Laboratoires de l’IBSAM : 1- CEMCA, UMR CNRS 6521

Résumé

Les deux dernières décennies ont été le témoin du développement incessant de substances organiques et de matériaux hybrides "organique-inorganique" dans le domaine de l’optoélectronique et de l’énergie, autorisant aujourd’hui l’accès à des diodes électroluminescentes et des sources laser à faible coût. Dans ce travail, nous avons présenté les propriétés optoélectroniques et le processus d’émission de lumière blanche d’une nouvelle pérovskite organique inorganique bidimensionnelle (2D).

In this work, we focus on the optoelectronic properties and white light emission process of a new two-dimensional (2D) organic−inorganic perovskite(C3H8N6)PbCl4. Its structure is determined by X-ray diffraction and it is built up from a stack of PbCl6 corner-sharing octahedral layers separated by organic melamine cations (C3H8N6)2+. Under UV excitation (300 nm), this material shows an intense quasi-white light emission; the photoluminescence spectrum shows a sharp line at 328 nm, characteristic of Wannier excitons in PbCl6 layers, and a broad band covering a wide range of the visible region and formed by the covering of four blue, green, yellow, and orange components at 470, 500, 555, and 595 nm, respectively. To analyze this multiexcitonic emission process, the synthesized crystals are characterized by optical absorption (OA), photoluminescence excitation (PLE), and time-resolved photoluminescence (TRPL) measurements. Simulations of the electronic band structure in terms of density functional theory (DFT) are also performed. These studies revealed that the two organic and inorganic phosphor sublattices have a very close highest occupied molecular orbital (HOMO)−lowest unoccupied molecular orbital (LUMO) band gap and form a type-II heterostructure system. In addition to the inorganic Wannier excitons (328 nm) and the singlet organic excitons (470 nm), the energy diagram describing the absorption and emission processes involves a self-trapped exciton, characteristic of the highly distorted PbCl6 octahedron layers (500 nm), as well as triplet organic excitons at around 555 and 595 nm. Furthermore, measurements of photoluminescence under variable excitation clearly demonstrate the enhancement of these emission peaks by Förster/Dexter resonance energy transfer in which the inorganic PbCl6 sheets act as donors and the organic cations act as acceptors.

MOTS CLES : Two-dimensional, Organic/Inoirganic, White-Light Emission