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Dilute magnetic semiconductors (DMSs) have attracted much attention because of their potential use in spintronic devices. Here, we demonstrate the observation of robust ferromagnetism in a solution-processable halide perovskite semiconductor with dilute magnetic ions. By codoping of magnetic (Fe2+) and aliovalent (Bi3+) metal ions into CH3NH3PbCl3 (MAPbCl(3)) perovskite, ferromagnetism with well-saturated magnetic hysteresis loops and a maximum coercivity field of 1280 Oe was observed below 12 K. The ferromagnetic resonance measurements revealed that the incorporation of aliovalent ions modulates the carrier concentration and plays an essential role in realizing the ferromagnetism in dilute magnetic halide perovskites. Magnetic ions are proposed to interact through itinerant charge carriers to achieve ferromagnetic coupling. Our work provides a new avenue for the development of solution-processable magnetic semiconductors.

Chiral hybrid Cu(I)-based iodides with d(10) closed shell demonstrate great potential for circularly polarized luminescence (CPL) because of high photoluminescence quantum yield (PLQY). Herein, by incorporating mono- or bi-dentate coordination mode ligands as chiral source, the self-assembly of four pairs of chiral hybrid Cu(I)-based iodides, namely, (R/S)-Cu4I4(Hmpy)(4)center dot H2O (R/S-1), (R/S)-Cu4I4(3Hpy)(4) (R/S-2), (R/S)-Cu4I4(2MePI)(4) (R/S-3), and (R/S)-Cu4I4(3AD)(4) (R/S-4) (where R/S-Hmpy = R/S-2-pyrrolidinemethanol, R/S-3Hpy = R/S-3-hydroxypyrrolidine, R/S-2MePI = R/S-2-methylpiperazine, and R/S-3AD = R/S-3-aminopiperidine), are reported. With the monodentate and bidentate ligands, these materials belong to two different structural types: 0D molecular clusters (R/S-1, R/S-2) and 3D porous metal-organic frameworks (R/S-3, R/S-4). These materials all crystallize in non-centrosymmetric space groups containing similar basic Cu4I4 cubane tetramer building units but with different coordination modes. They are also semiconductors, with optical bandgaps ranging from 2.70 to 2.94 eV. The photoluminescence (PL) and circularly polarized luminescence (CPL) emissions are further characterized, where the highest PLQY of approximate to 95% and CPL dissymmetry factor (g(lum)) of approximate to 7 x 10(-3) are achieved in R/S-1. This work offers a systematic comparison between different structural types with similar building blocks, bridging by the flexible chiral ligands, and shows that the hybrid copper iodides are highly promising candidates for next-generation optoelectronics and chiroptics.

Non-covalent interactions play an essential role in directing the self-assembly of hybrid organic–inorganic crystals. In hybrid halide perovskites, hydrogen bonding has been the paramount non-covalent interaction. Here, we show another non-covalent interaction, namely, the halogen bond interaction, that directs a symmetry-breaking assembly in a new series of two-dimensional (2D) perovskites (ICH2CH2NH3)2(CH3NH3)n−1PbnI3n+1 (n is the layer thickness, n=1–4). Structural analysis shows that the halogen bond strength varies with the layer thickness. For the odd number (n=1, 3) layered perovskites, stronger halogen interaction leads to centrosymmetric structures, whereas for the n=2 layered perovskites, weaker halogen bonds result in non-centrosymmetric structures. Transient reflection spectroscopy shows a suppressed radiative recombination rate (k2≈0) and prolonged spin lifetime for n=2 structure, suggesting an enhanced Rashba band splitting effect. The structural asymmetry is further confirmed with a reversible bulk photovoltaic effect. Our work provides a new design strategy to enable hybrid perovskites with emerging properties and functionalities associated with structural asymmetry.

Hybrid two-dimensional (2D) halide perovskites have emerged as an important class of high-performance semiconductors because of their excellent physical properties and structural diversity. Here, we report a new family of hybrid 2D Ge-based perovskites that have the Dion-Jacobson structure type, with the general formula A(MA)n-1GenX3n+1, where A = 2-(aminomethyl)pyridinium (2AMPY), 3-(aminomethyl)pyridinium (3AMPY), 4-(aminomethyl)pyridinium (4AMPY), or 4-(aminomethyl)piperidinium (4AMP), X = Br or I, and n = 1 or 2. Single-crystal X-ray diffraction shows that most of the bromide structures are centrosymmetric, whereas the iodide analogues are all non-centrosymmetric. The optical band gaps are effectively regulated by the level of octahedral distortion of the corresponding [GeX6], where a larger distortion corresponds to a larger band gap. These compounds exhibit relatively weak photoluminescence, which can be observed at low temperatures. All of the Ge-based iodide perovskites exhibit good second-harmonic generation (SHG) responses, with the highest reaching 0.53 × AgGaS2 for (4AMPY)GeI4, where their particle-dependent SHG has been investigated. First-principles calculations of the SHG properties are in good agreement with the experimental results. Furthermore, layer transformation can be achieved from the (100)- to (110)-oriented configuration by mixing the halides, which is a rare example. These results showcase the versatility and diversity of employing an asymmetric dication and the Ge2+ metal to achieve SHG active non-centrosymmetric materials, providing new strategies for the design of lead-free alternatives with interesting photophysical properties.

Hybrid organic–inorganic antimony halides have attracted increasing attention due to the non-toxicity, stability, and high photoluminescence quantum yield (PLQY). To shed light on the structural factors that contribute to the high PLQY, five pairs of antimony halides with general formula A2SbCl5 and A2Sb2Cl8 are synthesized via two distinct methods and characterized. The A2SbCl5 type adopts square pyramidal [SbCl5] geometry with near-unity PLQY, while the A2Sb2Cl8 adopts seesaw dimmer [Sb2Cl8] geometry with PLQY≈0 %. Through combined data analysis with the literature, we have found that A2SbCl5 series with square pyramidal geometry generally has much longer Sb⋅⋅⋅Sb distances, leading to more expressed lone pairs of SbIII. Additional factors including Sb−Cl distance and stability of antimony chlorides may also affect PLQY. Our targeted synthesis and correlated insights provide efficient tools to precisely form highly emissive materials for optoelectronic applications. © 2023 Wiley-VCH GmbH.

Introducing chirality into the metal-halide hybrids has enabled many emerging properties including chiroptical activity, spin-dependent transport, and ferroelectricity. However, most of the chiral metal-halide hybrids to date are non-emissive, and the underlying mechanism remains elusive. Here, we show a new strategy to turn on the circularly polarized luminescence (CPL) in chiral metal-halide hybrids. We demonstrate that alloying Sb3+ into chiral indium-chloride hybrids dramatically increases the photoluminescence quantum yield in two new series of chiral indium-antimony chlorides. These materials exhibit strong CPL signals with tunable energy and a high dissymmetry factor up to 1.5x10(-2). Mechanistic studies reveal that the emission originates from the self-trapped excitons centered in 5s(2) Sb3+. Moreover, near-ultraviolet pumped white light is demonstrated with a polarization up to 6.0 %. Our work demonstrates new strategies towards highly luminescent chiral metal-halide hybrids.

Low-dimensional metal halide perovskites are attracting extensive attention due to their enhanced quantum confinement and stability compared to three-dimensional perovskites. However, low dimensional connectivity in the inorganic frameworks leads to strongly bounded excitons with limited absorption properties, which impedes their application in photovoltaic devices. Here, we show that, by incorporating a strong electron accepting methylviologen cation, charge transfer (CT) at the organic/inorganic interface can effectively tune the optical properties in one-dimensional (1D) lead-halide perovskites. Both 1D MVPb2I6 and MVPb2Br6 display expanded absorption and photoresponse activity compared to CT inactive cations. The photoinduced CT process in MVPb2I6 was further characterized by transient absorption spectroscopy, which shows an ultrafast CT process within 1 ps, generating charge separated states. Our work unveils the interesting photophysics of these unconventional 1D perovskites with functional organic chromophores. © 2022 Author(s).