Multinuclear NMR as a tool for studying local order and dynamics in CH3NH3PbX3 (X = Cl, Br, I) hybrid perovskites

International audienceWe report on Pb, Br, N, H, C and H NMR experiments for studying the local order and dynamics in hybrid perovskite lattices. Pb NMR experiments conducted at room temperature on a series of MAPbX compounds (MA = CHNH; X = Cl, Br and I) showed that the isotropic Pb NMR shift is strongly dependent on the nature of the halogen ions. Therefore Pb NMR appears to be a very promising tool for the characterisation of local order in mixed halogen hybrid perovskites. Pb NMR on MAPbBrI served as a proof of concept. Proton, C and N NMR experiments confirmed the results previously reported in the literature. Low temperature deuterium NMR measurements, down to 25 K, were carried out to investigate the structural phase transitions of MAPbBr. Spectral lineshapes allow following the successive phase transitions of MAPbBr. Finally, quadrupolar NMR lineshapes recorded in the orthorhombic phase were compared with simulated spectra, using DFT calculated electric field gradients (EFG). Computed data do not take into account any temperature effect. Thus, the discrepancy between the calculated and experimental EFG evidences the fact that MA cations are still subject to significant dynamics, even at 25 K

Grafting Oligothiophenes on Surfaces by Diazonium Electroreduction: A Step toward Ultrathin Junction with Well-Defined Metal/Oligomer Interface

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Photophysics of self-assembled luminophore-perovskite systems

International audienceDuring the past few years hybrid organic-inorganic perovskites (HOIPs) have attracted much interest as solution-processed semiconductors with high potentialities in optoelectronics. On the one hand “3D” HOIPs such as CH3NH3PbI3 have shown their outstanding performances when incorporated in solar cells [1]. On the other hand their “2D layered” counterparts (R-NH3)2PbI4, where R is an organic group, are promising materials for light emitting devices such as LEDs [2] and Lasers [3]. Indeed their self-assembled, multilayered structure allows strong excitonic emission at room temperature (fig. 1). They offer moreover much flexibility with respect to the organic group R. While most of the reported 2D layered perovskites have optically inactive organic moieties, a huge improvement of the performances could be done by introducing functional organic groups. This is why we propose in the present work two innovative luminophore-perovskite systems. First by introducing 2,3-naphthalimide-ethylammonium (NAAB) fluorescent molecules in the perovskite structure we efficiently improved its excitonic emission [4]. Secondly thanks to the perovskite self-assembling we succesfully templated tetrazine molecules into the perovskite structure and changed their optical properties (fig. 2)

Fast growth of monocrystalline thin films of 2D layered hybrid perovskite

International audienceDuring the past few years hybrid organic-inorganic perovskites (HOIPs) have attracted much interest as solution-processed semiconductors with high potentialities in optoelectronics and photovoltaics. On the one hand 3D HOIPs such as CH3NH3PbI3 have shown their outstanding performances when incorporated in solar cells [1]. On the other hand their 2D layered counterparts such as (C6H5C2H4NH3)2PbI4 (PEPI) are promising materials for light emitting devices because of their strong emission at room temperature [2]. However, the optoelectronic properties of hybrid perovskite polycrystalline films suffer from a microscale grain structure. In order to take advantage of the great potential of these materials for both photovoltaics and emitting devices, the synthesis of large monocrystalline films is a key issue. Here we propose a fast crystallization method for the 2D layered hybrid perovskite PEPI. A vapor-assisted process coupled with a capping of the precursor solution allows to grow 2-dimensionnal thin films with millimetric monocrystalline grains, a high aspect ratio and a good surface quality (Fig.1). Moreover, this growth is several orders of magnitudes faster than the other reported techniques. In addition, we highlight the benefits of using γ-butyrolactone (GBL) for the growth of layered perovskites monocrystalline grains

Fast growth of monocrystalline thin films of 2D layered hybrid perovskite

International audienceHybrid organic-inorganic perovskites are on the way to deeply transform the photovoltaic domain. Likewise, it recently appears that this class of materials have a lot of assets for other optoelectronic applications. One key aspect is to be able to synthesize large areas of monocrystalline thin films. Here, we report on the development of a new synthesis method of 2D hybrid organic-inorganic perovskite called "Anti-solvent Vapor-assisted Capping Crystalliza-tion". This method allows to grow monocrystalline thin films with high aspect ratio in less than 30 minutes

Single-walled carbon nanotube/polystyrene core-shell hybrids: synthesis and photoluminescence properties

International audienceThe formation of core-shell structures has permitted to improve greatly the emission properties of inorganic quantum dots. Single-Walled Carbon Nanotubes, thanks to their emission in the near infrared region, are promising materials for optoelectronics. However, the extreme sensitivity of nanotubes to their environment hinders their applications. Thus, the fabrication of tailor-made functional hybrid materials that preserve the optical properties of SWNTs and facilitate their manipulation is extremely important. Here, we describe the synthesis of core-shell nanotube materials made of SWNTs and polystyrene. We developed a two-step strategy that permits to form a stable and homogeneous layer of polymer around the nanotubes by adding first polystyrene via the micelle swelling method and then by locking the structure via radical polymerisation in micelles of styrene and divinylbenzene. After polymerisation and redispersion, the nanotube hybrids can be easily manipulated in solution; they still exhibited photoluminescence properties both in solution and in the solid state demonstrating that the SWNTs embedded in their polystyrene shell are isolated one from each other

Photophysics of self-assembled luminophore-perovskite systems

International audienceDuring the past few years hybrid organic-inorganic perovskites (HOIPs) have attracted much interest as solution-processed semiconductors with high potentialities in optoelectronics. On the one hand “3D” HOIPs such as CH3NH3PbI3 have shown their outstanding performances when incorporated in solar cells [1]. On the other hand their “2D layered” counterparts (R-NH3)2PbI4, where R is an organic group, are promising materials for light emitting devices such as LEDs [2] and Lasers [3]. Indeed their self-assembled, multilayered structure allows strong excitonic emission at room temperature (fig. 1). They offer moreover much flexibility with respect to the organic group R. While most of the reported 2D layered perovskites have optically inactive organic moieties, a huge improvement of the performances could be done by introducing functional organic groups. This is why we propose in the present work two innovative luminophore-perovskite systems. First by introducing 2,3-naphthalimide-ethylammonium (NAAB) fluorescent molecules in the perovskite structure we efficiently improved its excitonic emission [4]. Secondly thanks to the perovskite self-assembling we succesfully templated tetrazine molecules into the perovskite structure and changed their optical properties (fig. 2)

Micro-photoluminescence study of 2D-layered hybrid perovskite monocrystalline thin films. Correlation between the structural and optoelectronics properties

International audienceOver the past few years, organic-inorganic halide 3D perovskites (3D-HOP) were found to present remarkable optoelectronic properties. A great attention has been paid to perovskites thin films, as an ideal building block for PV and LED devices. On the other hand, the study of single crystals has proven necessary to unveil some of the intrinsic properties of these semiconductors [1,2]. While the 2D perovskites have been known for decades, they are attracting growing interest, for their strong PL properties, their chemical versatility and their low sensitivity to external degradation mechanisms due to UV light and moisture. Monocrystalline thin films of phenylethylammonium-based 2D perovskites (C 6 H 5 C 2 H 4 NH 3) 2 PbI 4 and their 2D/3D derivatives are produced using the "Anti-solvent Vapor Assisted Capping Crystalllization [3]. A cryogenic micro-photoluminescence study of these samples will be presented (with a sub micrometer precision), allowing to extract the intrinsic properties of the perovskite crystals, such as electron-phonon coupling and the PL lifetimes. This technique allows in particular to finely correlate the optoelectronic properties of the produced films with their morphology. The optoelectronic properties of these monocrystalline thin films will be compared to the ones of spin-coated polycrystalline perovskites films. They will be also compared to the ones published on butylammonium-based 2D perovskites, that were recently used to create efficient and longed-lived solar cells [4]

Micro-photoluminescence study of 2D-layered perovskites crystals and thin films. Correlation between the structural and optoelectronics properties.

International audienceOver the past few years, organic inorganic halide 3D perovskites (3D-HOP) were found to present remarkable optoelectronic properties. A great attention has been paid to perovskites thin films, as an ideal building block for PV and LED devices. On the other hand, the study of single crystals has proven necessary to unveil some of the intrinsic properties of these semiconductors [1,2]. While the 2D perovskites have been known for decades, there is growing interesting their structure, for their strong PL properties, their chemical versatility and their low sensitivity to external degradation mechanisms (due to UV light, water,…). In this poster, we will study the optical properties of phenylethylammonium based 2D perovskites (C6H5C2H4NH3)2PbI4 and their 2d/3d derivatives. A cryogenic micro-photoluminescence study will be presented (with a sub micrometer precision). This technique allows to finely correlate the optoelectronic properties (excitons/phonons, …) of the produced films with their morphology. These properties are then compared to the ones of spin coated polycrystalline perovskites films. This study allows to extract the intrinsic properties of the perovskites crystals (electron phonon/ coupling, Pl lifetimes). Finally, we will also compare our results to the one published on butylammonium based 2D perovskites, that were recently used to create efficient and longed-lived solar cells [3], despite their large binding energies