Photoluminescence and spin selectivity in chiral layered halide perovskites

International audienceIf 3-dimensional (3D) halide perovskites AMX3 (A: organic cation, M: metal ion, X: halide) have shown spectacular results in optoelectronic devices, they offer limited choice of metals and organic cations. This is not the case of the other shapes that impose far less constraints over the chemical design of the organic spacer, such as layered (2D) halide perovskites (LHPs) [1]. The optical properties of those materials are marked by strong excitonic features that can be tuned by materials engineering over the chemical nature of the metals [2] or the organic spacer [3]. Excitonic properties can also be modified by controlling the structural properties of LHPs guided by the concept of lattice mismatch recently proposed [4]. Finally, the optical properties of LHPs can be enriched by substituting the optically-inert organic spacer by a chiral cation, leading to high responses for circularly polarized absorption and emission, but also spin selectivity through the materials [5]. Here, we will show how modeling and computational investigations can contribute to the writing of guidelines for the design of optimized LHPs for optoelectronic and spintronic applications.Acknowledgment. The work at ISCR and Institut FOTON was performed with funding from the European Union’s Horizon 2020 program, through an innovation action under grant agreement no. 861985 (PeroCUBE) and through a FET Open research and innovation action under the grant agreement no. 899141 (PoLLoC). This work was granted access to the HPC resources of TGCC under the allocations 2022-A0130907682 made by GENCI.[1]B. Saparov, D. B. Mitzi, Chem. Rev. 2016, 116, 4558; L. Pedesseau, M.K. et al., ACS Nano 2016, 10, 9776; C. Katan, N. Mercier, J. Even, Chem. Rev. 2019, 119, 3140.[2]P. Fu, M.K. et al., J. Am. Chem. Soc. 2023, in press.[3]E. S. Vasileiadou, M.K. et al., J. Am. Chem. Soc. 2022, 144, 6390.[4]M. Kepenekian et al., Nano Lett. 2018, 18, 5603; E. S. Vasileiadou, M.K. et al., Chem. Mater. 2021, 33, 5085.[5]S. Liu, M.K. et al., submitted manuscript; A. Abhervé, M.K. et al., submitted manuscript

Chirality-induced spin selectivity and chiroptical properties in layered halide perovskites

International audience3-dimensional (3D) halide perovskites AMX3 (A: organic cation, M: metal ion, X: halide) have shown spectacular results in optoelectronic devices. However, they offer limited choice of metals and organic cations, which limits the chemical design of optimal materials. This is not the case of lower dimensional materials, e.g. layered (2D) halide perovskites (LHPs) [1], that impose far less constraints over the organic spacer. It then become possible to associate the exceptional optoelectronic properties of halide perovskites with chiral cations to reach promising materials for chiroptical and magnetochiral applications [2].Here, we report joint experimental and theoretical investigations of LHPs with exceptional (i) chiroptical, and (ii) magnetochiral properties. Firstly, the enantiopure 3BrMBA2PbI4 (MBA = methylbenzylammonium) perovskite thin films exhibit external photoluminescence quantum efficiency as high as 39% and circularly polarized photoluminescence up to 52%, at room temperature [3]. Next, we consider a series of chiral lead-bromide networks which crystallize in enantiomorphic polar space groups P41212 and P43212 for the R and S enantiomers, respectively [4]. Chirality-induced spin selectivity (CISS) effect measurements performed over those materials by magnetic conducting-probe atomic force microscopy (mc-AFM) reveal a spin polarization of about 40% [4].We use a set of experimental characterizations (e.g. single-crystal x-ray diffraction), and theoretical tools (semi-empirical modeling and density-functional theory based calculations) to describe the chiral-related properties of these LHPs and help the cation engineering of efficient chiral halide perovskites.Acknowledgment. The work was performed with funding from Agence Nationale pour la Recherche under grant ANR-18-CE05-0026 (MORELESS project), the European Union’s Horizon 2020 program, through an innovation action under grant agreement no. 861985 (PeroCUBE) and a FET Open research and innovation action under the grant agreement no. 899141 (PoLLoC). This work was granted access to the HPC resources of TGCC under the allocations 2022-A0130907682 made by GENCI.[1]B. Saparov, D. B. Mitzi, Chem. Rev. 2016, 116, 4558; L. Pedesseau, M.K. et al., ACS Nano 2016, 10, 9776; C. Katan, N. Mercier, J. Even, Chem. Rev. 2019, 119, 3140.[2]Y.-H. Kim et al., Science 2021, 371, 1129 ; M. K. Jana et al., Nat. Commun. 2021, 12, 4982 ; G. Long et al., Nat. Rev. Mater. 2020, 5, 423 ; H. Lu, Z. V. Vardeny, M. C. Beard, Nat. Rev. Chem. 2022, 6, 470.[3]S. Liu, M.K. et al., submitted manuscript.[4]A. Abhervé, M.K. et al., submitted manuscript

Regulation of the Psoriatic Chemokine CCL20 by E3 Ligases Trim32 and Piasy in Keratinocytes

Psoriasis is an inflammatory skin disorder with aberrant regulation of keratinocytes and immunocytes. Although it is well known that uncontrolled keratinocyte proliferation is largely driven by proinflammatory cytokines from the immunocytes, the functional role of keratinocytes in the regulation of immunocytes is poorly understood. Recently, we found that tripartite motif-containing protein 32 (Trim32), an E3-ubiquitin ligase, is elevated in the epidermal lesions of human psoriasis. We previously showed that Trim32 binds to the protein inhibitor of activated STAT-Y (Piasy) and mediates its degradation through ubiquitination. Interestingly, the Piasy gene is localized in the PSORS6 susceptibility locus on chromosome 19p13, and Piasy negatively regulates the activities of several transcription factors, including NF-κB, STAT, and SMADs, that are implicated in the pathogenesis of psoriasis. In this study, we show that Trim32 activates, and Piasy inhibits, keratinocyte production of CC chemokine ligand 20 (CCL20), a psoriatic chemokine essential for recruitment of DCs and T helper (Th)17 cells to the skin. Further, Trim32/Piasy regulation of CCL20 is mediated through Piasy interaction with the RelA/p65 subunit of NF-κB. As CCL20 is activated by Th17 cytokines, the upregulation of CCL20 production by Trim32 provides a positive feedback loop of CCL20 and Th17 activation in the self-perpetuating cycle of psoriasis

Photoexcitation Control of Excitation Relaxation in Mixed‐Phase Ruddlesden‐Popper Hybrid Organic‐Inorganic Lead‐Iodide Perovskites

AbstractThe electronic states and exciton binding energies of layered Ruddlesden‐Popper (RP) metal‐halide perovskites can be tailored through changes of their chemical composition, yielding multi‐phase systems with complex energy cascades. Ultrafast photoexcitation relaxation with transfer dynamics into domains of increasing layer number has been reported for these materials. Here, ultrafast optical spectroscopy is used to report an unexpected excitation energy dependence of photoexcitation relaxation dynamics in mixed‐dimensional benzylammonium cesium lead iodide RP perovskite (BeA2CsPb2I7) thin films, which gives rise to spectrally broadband luminescence over the visible region. Using transient absorption and photoluminescence spectroscopy it is found that excitations, which are formed in the n  =  2 RP‐phase after photoexcitation with ≈0.2 electron volt excess energy, transfer to higher layer number RP‐phases on unexpectedly slow timescales of tens of picoseconds. Further, it is observed that such excitations are initially optically passive. Notably, luminescence occurs under these conditions from multiple RP‐phases with optical bandgaps across the visible range, yielding broadband luminescence. The results hold potential for realization of broadband white‐light emitters and other light‐emitting devices.</jats:p

Bright circularly polarized photoluminescence in chiral layered hybrid lead-halide perovskites.

Hybrid perovskite semiconductor materials are predicted to lock chirality into place and encode asymmetry into their electronic states, while softness of their crystal lattice accommodates lattice strain to maintain high crystal quality with low defect densities, necessary for high luminescence yields. We report photoluminescence quantum efficiencies as high as 39% and degrees of circularly polarized photoluminescence of up to 52%, at room temperature, in the chiral layered hybrid lead-halide perovskites (R/S/Rac)-3BrMBA2PbI4 [3BrMBA = 1-(3-bromphenyl)-ethylamine]. Using transient chiroptical spectroscopy, we explain the excellent photoluminescence yields from suppression of nonradiative loss channels and high rates of radiative recombination. We further find that photoexcitations show polarization lifetimes that exceed the time scales of radiative decays, which rationalize the high degrees of polarized luminescence. Our findings pave the way toward high-performance solution-processed photonic systems for chiroptical applications and chiral-spintronic logic at room temperature

Strong Induced Circular Dichroism in a Hybrid Lead‐Halide Semiconductor Using Chiral Amino Acids for Crystallite Surface Functionalization

Chirality is a desired property in functional semiconductors for optoelectronic, catalytic, and spintronic applications. Here, introducing enantiomerically-pure 3-aminobutyric acid (3-ABA) into thin films of the 1D semiconductor dimethylammonium lead iodide (DMAPbI$_3$) is found to result in strong circular dichroism (CD) in the optical absorption. X-ray diffraction and grazing incidence small angle X-ray scattering (GISAXS) are applied to gain molecular-scale insights into the chirality transfer mechanism, which is attributed to a chiral surface modification of DMAPbI$_3$ crystallites. This study demonstrates that the CD signal strength can be controlled by the amino-acid content relative to the crystallite surface area. The CD intensity is tuned by the composition of the precursor solution and the spin-coating time, thereby achieving anisotropy factors (g$_{abs}$) as high as 1.75 × 10$^{–2}$. Grazing incidence wide angle scattering reveals strong preferential ordering that can be suppressed via tailored synthesis conditions. Different contributions to the chiroptical properties are resolved by a detailed analysis of the CD signal utilizing an approach based on the Mueller matrix model. This report of a novel class of chiral hybrid semiconductors with precise control over their optical activity presents a promising approach for the design of circularly polarized light detectors and emitters

Motional Narrowing Effects in the Excited State Spin Populations of Mn-Doped Hybrid Perovskites

Spin–orbit coupling in the electronic states of solution-processed hybrid metal halide perovskites forms complex spin-textures in the band structures and allows for optical manipulation of the excited state spin-polarizations. Here, we report that motional narrowing acts on the photoexcited spin-polarization in CH3NH3PbBr3 thin films, which are doped at percentage-level with Mn2+ ions. Using ultrafast circularly polarized broadband transient absorption spectroscopy at cryogenic temperatures, we investigate the spin population dynamics in these doped hybrid perovskites and find that spin relaxation lifetimes are increased by a factor of 3 compared to those of undoped materials. Using quantitative analysis of the photoexcitation cooling processes, we reveal increased carrier scattering rates in the doped perovskites as the fundamental mechanism driving spin-polarization-maintaining motional narrowing. Our work reports transition-metal doping as a concept to extend spin lifetimes of hybrid perovskites