Perovskite Light-Emitting Devices - Fundamentals and Working Principles

Temperature dependence of Photoluminescence and Amplified Spontaneous Emission in thin films of quasi-2D BA3MA3Pb5Br16 perovskites

Dual-source vacuum deposition of pure and mixed halide 2D perovskites: thin film characterization and processing guidelines

The dual-source vacuum deposition of 2D perovskite films of the type PEA2PbX4, (PEA = phenethylammonium and X = I−, Br−, or a combination of both) is presented. Low-temperature deposited 2D perovskite films showed high crystallinity with the expected trend of bandgap as a function of halide type and concentration. Importantly, we observed an unavoidable halide cross-contamination among different deposition runs, as well as a strong dependence of the material quality on the type of halide precursors used. These findings should be taken into account in the development of vacuum processing for low-dimensional mixed halide perovskites.

Highly Stable Red-Light-Emitting Electrochemical Cells

The synthesis and characterization of a series of new cyclometalated iridium(III) complexes [Ir(ppy) 2 (N ∧ N)][PF 6 ] in which Hppy = 2-phenylpyridine and N ∧ N is (pyridin-2-yl)benzo[ d ]thiazole ( L1 ), 2-(4-( tert -butyl)pyridin-2-yl)benzo[ d ]thiazole ( L2 ), 2-(6-phenylpyridin-2-yl)benzo[ d ]thiazole ( L3 ), 2-(4-( tert -butyl)-6-phenylpyridin-2-yl)benzo[ d ]thiazole ( L4 ), 2,6-bis(benzo[ d ]thiazol-2-yl)pyridine ( L5 ), 2-(pyridin-2-yl)benzo[ d ]oxazole ( L6 ), or 2,2′-dibenzo[ d ]thiazole ( L7 ) are reported. The single crystal structures of [Ir(ppy) 2 ( L1 )][PF 6 ]·1.5CH 2 Cl 2 , [Ir(ppy) 2 ( L6 )][PF 6 ]·CH 2 Cl 2 , and [Ir(ppy) 2 ( L7 )][PF 6 ] have been determined. The new com…

Solution processed organic light-emitting diodes using a triazatruxene crosslinkable hole transporting material.

A cross-linkable triazatruxene that leads to insoluble films upon thermal annealing at temperatures compatible with flexible substrates is presented. The films were used as the hole transporting and electron blocking layer in partially solution processed phosphorescent organic light-emitting diodes, reaching power conversion efficiencies of 24 lm W−1, an almost 50% improvement compared to the same OLEDs without the cross-linkable hole transporting layer.

Vacuum Deposited Triple-Cation Mixed-Halide Perovskite Solar Cells

Hybrid lead halide perovskites are promising materials for future photovoltaics applications. Their spectral response can be readily tuned by controlling the halide composition, while their stability is strongly dependent on the film morphology and on the type of organic cation used. Mixed cation and mixed halide systems have led to the most efficient and stable perovskite solar cells reported, so far they are prepared exclusively by solution-processing. This might be due to the technical difficulties associated with the vacuum deposition from multiple thermal sources, requiring a high level of control over the deposition rate of each precursor during the film formation. In this report, the…

A new cross-linkable 9,10-diphenylanthracene derivative as a wide bandgap host for solution-processed organic light-emitting diodes

Efficient organic light-emitting diodes (OLEDs) can be obtained using multilayered architectures where the processes of charge injection, transport and recombination are separated and optimized in each layer. Processing these structures from solution requires strategies to avoid redissolution or damage of the previously deposited layers. Several reports have demonstrated the development of cross-linkable hole transport materials, while less literature describes the synthesis and applications of such wide bandgap host materials for multilayered OLEDs. In this work we introduce a cross-linkable derivative of 9-(4-(10-phenylanthracene-9-yl)phenyl)-9H-carbazole incorporating styrene moieties (S…

Vacuum-Deposited 2D/3D Perovskite Heterojunctions

Low-dimensional (quasi-) 2D perovskites are being extensively studied in order to enhance the stability and the open-circuit voltage of perovskite solar cells. Up to now, thin 2D perovskite layers on the surface and/or at the grain boundaries of 3D perovskites have been deposited solely by solution processing, leading to unavoidable intermixing between the two phases. In this work, we report the fabrication of 2D/3D/2D perovskite heterostructures by dual-source vacuum deposition, with the aim of studying the interaction between the 3D and 2D phases as well as the charge transport properties of 2D perovskites in neat 2D/3D interfaces. Unlike what is normally observed in solution-processed 3D…

Amplified spontaneous emission in thin films of quasi-2D BA3MA3Pb5Br16 lead halide perovskites

Quasi-2D (two-dimensional) hybrid perovskites are emerging as a new class of materials with high photoluminescence yield and improved stability compared to their three-dimensional (3D) counterparts. Nevertheless, despite their outstanding emission properties, few studies have been reported on amplified spontaneous emission (ASE) and a thorough understanding of the photophysics of these layered materials is still lacking. In this work, we investigate the ASE properties of multilayered quasi-2D BA3MA3Pb5Br16 films through the dependence of the photoluminescence on temperature and provide a novel insight into the emission processes of quasi-2D lead bromide perovskites. We demonstrate that the …

Impact of the use of sterically congested Ir(III) complexes on the performance of light-emitting electrochemical cells

International audience; The synthesis, structural and optoelectronic characterization of a family of sterically congested cyclometalated cationic Ir(iii) complexes of the form [Ir(C^N)2(dtBubpy)]PF6 (with dtBubpy = 4,4′-di-tert-butyl-2,2′-bipyridine and C^N = a cyclometalating ligand decorated at the 4-position of the pyridine ring and/or the 3-position of the phenyl ring with a range of sterically bulky substituents) are reported. This family of complexes is compared to the unsubstituted analogue complex R1 bearing 2-phenylpyridinato as cyclometalating ligand. The impact of sterically bulky substituents on the C^N ligands on both the solid state photophysics and light-emitting electrochemi…

CF3 Substitution of [Cu(P^P)(bpy)][PF6 ] Complexes: Effects on Photophysical Properties and Light-Emitting Electrochemical Cell Performance

Herein, [Cu(P^P)(N^N)][PF6 ] complexes (P^P=bis[2-(diphenylphosphino)phenyl]ether (POP) or 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene (xantphos); N^N=CF3 -substituted 2,2'-bipyridines (6,6'-(CF3 )2 bpy, 6-CF3 bpy, 5,5'-(CF3 )2 bpy, 4,4'-(CF3 )2 bpy, 6,6'-Me2 -4,4'-(CF3 )2 bpy)) are reported. The effects of CF3 substitution on their structure as well as their electrochemical and photophysical properties are also presented. The HOMO-LUMO gap was tuned by the N^N ligand; the largest redshift in the metal-to-ligand charge transfer (MLCT) band was for [Cu(P^P){5,5'-(CF3 )2 bpy}][PF6 ]. In solution, the compounds are weak yellow to red emitters. The emission properties depend on the substitu…

Ruthenium pentamethylcyclopentadienyl mesitylene dimer: a sublimable n-dopant and electron buffer layer for efficient n-i-p perovskite solar cells

Electron-transport materials such as fullerenes are widely used in perovskite solar cells to selectively transfer the photogenerated electrons to the electrodes. In order to minimize losses at the interface between the fullerene and the electrode, it is important to reduce the energy difference between the transport level of the two materials. A common approach to reduce such energy mismatch is to increase the charge carrier density in the semiconductor through doping. A variety of molecular dopants have been reported to reduce (n-dope) fullerenes. However, most of them are either difficult to process or extremely air sensitive, with most n-dopants leading to the formation of undesirable si…

Enamine-based hole transporting materials for vacuum-deposited perovskite solar cells

In a short period of time, the rapid development of perovskite solar cells attracted a lot of attention in the science community with the record for power conversion efficiency being broken every year. Despite the fast progress in power conversion efficiency there are still many issues that need to be solved before starting large scale commercial applications, such as, among others, the difficult and costly synthesis and usage of toxic solvents for the deposition of hole transport materials (HTMs). We herein report new enamine-based charge transport materials obtained via a simple one step synthesis procedure, from commercially available precursors and without the use of expensive organomet…

Front Cover: CF3 Substitution of [Cu(P^P)(bpy)][PF6 ] Complexes: Effects on Photophysical Properties and Light-Emitting Electrochemical Cell Performance (ChemPlusChem 4/2018)

Deep-blue thermally activated delayed fluorescence (TADF) emitters for light-emitting electrochemical cells (LEECs)

The authors acknowledge the University of St Andrews for financial support. The authors also acknowledge financial support from the European Union H2020 project INFORM (grant 675867), the Spanish Ministry of Economy and Competitiveness (MINECO) via the Unidad de Excelencia María de Maeztu MDM-2015-0538, MAT2014-55200 and the Generalitat Valenciana (Prometeo/2016/135). MLP acknowledges support from a Grisolia grant (GRISOLIA/2015/A/146). Two deep blue thermally activated delayed fluorescence (TADF) emitters ( imCzDPS and imDPADPS ) that contain charged imidazolium groups tethered to the central luminophore were designed and synthesized as small molecule organic emitters for light-emitting e…

Efficient photoluminescent thin films consisting of anchored hybrid perovskite nanoparticles

Methylammonium lead bromide nanoparticles are synthetized with a new ligand (11-aminoundecanoic acid hydrobromide) by a non-template method. Upon dispersion in toluene they show a remarkable photoluminescence quantum yield of 80%. In addition, the bifunctional ligand allows anchoring of the nanoparticles on a variety of conducting and semiconducting surfaces, showing bright photoluminescence with a quantum yield exceeding 50%. This opens a path for the simple and inexpensive preparation of multilayer light-emitting devices. NRF (Natl Research Foundation, S’pore) ASTAR (Agency for Sci., Tech. and Research, S’pore) Accepted version

CCDC 1515402: Experimental Crystal Structure Determination

Related Article: Cristina Momblona, Cathrin D. Ertl, Antonio Pertegás, José M. Junquera-Hernández, Maria-Grazia La-Placa, Alessandro Prescimone, Enrique Ortí, Catherine E. Housecroft, Edwin C. Constable, and Henk J. Bolink|2017|J.Am.Chem.Soc.|139|3237|doi:10.1021/jacs.6b13311

CCDC 1515401: Experimental Crystal Structure Determination

Related Article: Cristina Momblona, Cathrin D. Ertl, Antonio Pertegás, José M. Junquera-Hernández, Maria-Grazia La-Placa, Alessandro Prescimone, Enrique Ortí, Catherine E. Housecroft, Edwin C. Constable, and Henk J. Bolink|2017|J.Am.Chem.Soc.|139|3237|doi:10.1021/jacs.6b13311

CCDC 1062206: Experimental Crystal Structure Determination

Related Article: Cristina Momblona, Cathrin D. Ertl, Antonio Pertegás, José M. Junquera-Hernández, Maria-Grazia La-Placa, Alessandro Prescimone, Enrique Ortí, Catherine E. Housecroft, Edwin C. Constable, and Henk J. Bolink|2017|J.Am.Chem.Soc.|139|3237|doi:10.1021/jacs.6b13311

Deep-Blue Thermally Activated Delayed Fluorescence (TADF) Emitters for Light-Emitting Electrochemical Cells (LEECs) (dataset)