LASER & PHOTONICS REVIEWS.08 February 2023.https://doi.org/10.1002/lpor.202200999

For the conventional persistent luminescence (PersL) charging processes, carriers are photo-pumped to the conduction band (CB) or high-energy excited states (HES) under short-wavelength UV or coherent near-infrared (NIR) laser excitation. Herein, electron tunneling charging behavior is reported in Cr³⁺, Sm³⁺ co-doped NIR PersL magnetoplumbite SrGa₁₂O₁₉, which allows for efficient charging by incoherent visible light. First, the electrons are efficiently captured by the neighboring Ga^II-O²⁻ electron–hole trap centers via a tunneling process, and then these excited electrons are transferred to shallow traps via a persistently energetic optical pump. This work further optimizes the PersL performance via engineering the energy band through partial substitution of In³⁺ for Ga³⁺. Consequently, tunneling charging occurring near the neighboring Cr³⁺-traps dimers enables Sr(Ga,In)₁₂O₁₉:Cr³⁺,Sm³⁺ to display brighter NIR PersL (≈760 nm, peak; ≈100 nm, FWHM) than gallate spinel under sunlight irradiation. This work provides insights into electron tunneling charging under low-energy excitation for NIR PersL, which may inspire more PersL explorations for practical applications.

ADVANCED OPTICAL MATERIALS.27 April 2023.https://doi.org/10.1002/adom.202300218

Organic–inorganic metal halides (OIMHs) with high-efficiency solar spectrum-like emission are attracting broad and current interest. Here, five 0D Zn-based hybrid halides are synthesized based on aromatic organic cations with different carbon-chain lengths: C₆H₅CH₂NH₃⁺ (PMA⁺) and C₆H₅(CH₂)₄NH₃⁺ (PBA⁺). (PMA)₂ZnCl₄ exhibits the highest photoluminescence quantum yield of 37.2% of reported Zn-based white-emission OIMHs. The emission spectrum of (PBA)₂ZnI₄ indicates a color rendering index of 98, which is the highest among single-component white-light-emitting phosphors. Spectral characterizations and density functional theory calculations demonstrate that the extremely broad emission of (PBA)₂ZnI₄ originates from the synergistic emission of organic cations and self-trapped excitons. The optical properties of the obtained (PMA)₂ZnBr₄, (PMA)₂ZnI₄·H₂O, and (PBA)₂ZnCl₄ are also characterized for comparison, and with the same organic cations, the PLQY decreases from chloride to bromide to iodide. This work demonstrates that the selection of appropriate organics and halogens can enable fine tuning of single-component white-light emission, satisfying varying needs for solid-state lighting.

Inorg. Chem. 2022, 61, 19, 7560–7567.https://doi.org/10.1021/acs.inorgchem.2c00711

Organic–inorganic metal halides (OIMHs) exhibit excellent photoelectric properties; however, their high-temperature light-emission stability requires further improvement. Here, we report three isostructural OIMHs (C₂H₈N)₄InCl₇, (C₂H₈N)₄SbCl₇, and (C₂H₈N)₄SbBr₇ (C₂H₈N⁺ = dimethylammonium). They are all crystallized in the P2₁2₁2 space group with a zero-dimensional (0D) structure, with orange-red photoluminescence (PL) under 365 nm UV excitation. Among them, (C₂H₈N)₄InCl₇ exhibits the strongest PL with a photoluminescence quantum yield (PLQY) of 13.9% at room temperature. Optical property measurements and density functional theory unveil that the luminescence of (C₂H₈N)₄InCl₇ at 405 and 620 nm is due to free exciton and self-trapped exciton emission, respectively. It is worth noting that (C₂H₈N)₄InCl₇ shows a high PL quenching temperature, maintaining 50% of its room-temperature PL intensity at 425 K, which is rare in OIHMs. This is much higher than the application temperature of phosphors in practical solid-state lighting applications (363–383 K). In this temperature range, the luminous intensity of (C₂H₈N)₄InCl₇ exceeds 60% of that at room temperature. The high PL quenching temperature observed in (C₂H₈N)₄InCl₇ indicates the potential of OIMHs for applications in phosphor-converted light-emitting diodes.

Inorg. Chem. Front., 2022,9, 3865-3873.https://doi.org/10.1039/D2QI00884J

Lead-based organic–inorganic metal halides (OIMHs) have recently attracted special attention due to their efficient broadband photoluminescence. However, the toxicity of lead poses a challenge for their further development. Here, we selected Sn(IV) as the metal center to synthesize the environmentally friendly and stable luminescent OIMHs (C₉H₁₅N₃)₂SnCl₈ and (C₉H₁₅N₃)₂SnBr₈ (C₉H₁₃N₃ is 1-(2-pyridyl)piperazine). Both compounds possess zero-dimensional structures, crystallizing in the monoclinic space group P2₁/c, and their optical band gaps were experimentally determined to be 3.19 and 2.60 eV, respectively. Under UV excitation at room temperature, (C₉H₁₅N₃)₂SnCl₈ exhibited double-peak emissions centered at 405 and 688 nm, which were attributed to the organic cation and inorganic octahedra, respectively. Upon introducing 5s²-lone-pair-containing Sb³⁺ in (C₉H₁₅N₃)₂SnCl₈, self-trapped emission was promoted, and the photoluminescence quantum yield increased from ∼1% to ∼17.84%. This work suggests effective strategies for finding environmentally friendly stable OIMHs and for further enhancing the luminescence properties through lone-pair-containing cation doping.

Inorg. Chem. 2022, 61, 38, 15016–15022,https://doi.org/10.1021/acs.inorgchem.2c01900

Recently, excellent optical properties of low-dimensional organic–inorganic metal halides, stemming from their tunable structure and optoelectronic properties, have been demonstrated. The synthetic method is critical because it is highly related to the structure and properties of the halide. Herein, we obtain two different antimony bromides, (Bmpip)₂SbBr₅ and (Bmpip)₃Sb₂Br₉, which both possess the P2₁/c space group having different crystal structures, and this confirms the important influence of synthesis on the single-crystal structure. (Bmpip)₂SbBr₅ contains Bmpip⁺ and [SbBr₅]^2– pyramids, and (Bmpip)₃Sb₂Br₉ consists of Bmpip⁺ and Sb-based dimers [Sb₂Br₉]^3–. Under 400 nm excitation, (Bmpip)₂SbBr₅ exhibits a 640 nm orange emission with a quantum yield of ∼11.5% owing to Sb 5s² electron luminescence. A diode was fabricated by (Bmpip)₂SbBr₅ and commercial phosphors and showed a high color render index of 92. Our work reveals the effect of the preparation method on the crystal structure. A luminescent material was finally identified.

Inorg. Chem. 2022, 61, 30, 11973–11980.https://doi.org/10.1021/acs.inorgchem.2c01730

The participation of organic cations plays an important role in tuning broad-spectra emissions. Herein, we synthesized a series of Mn(II)-based two-dimensional (2D) halide perovskites with arylamine cations of different lengths having the general formula (C₆H₅(CH₂)_xNH₃)₂MnCl₄ (x = 1–4), with the x = 4 compound reported here for the first time. With the increase in the −(CH₂)– in organic cations, the distance between adjacent inorganic layers increases, causing the title compounds to exhibit different structural distortions. As the Mn–Cl–Mn angular distortion increases, the experimental optical band gaps of the title compounds increase correspondingly. When the angle distortion between the octahedrons of the compounds is similar, the band gaps may also be affected by the distortion of the octahedron itself (the bond-length distortion of 2 is greater than that of 4). Under UV-light irradiation at 298 K, all of the compounds exhibit two emission peaks centered at 480–505 and 610 nm, corresponding to the organic-cation emission and the ⁴T₁(G) to ⁶A₁(S) radiative transition of Mn²⁺ ions, respectively. Among these title compounds, (PPA)₂MnCl₄ [(PPA)⁺ = C₆H₅(CH₂)₃NH₃⁺] exhibits the strongest photoluminescence (PL). The study of the title compounds contributes to an in-depth understanding of the relationship between the structural distortion and optical properties of 2D Mn(II)-based perovskite materials.

Inorg. Chem. 2023, 62, 31, 12501–12509.https://doi.org/10.1021/acs.inorgchem.3c01726

Organic–inorganic metal halides (OIMHs) have various crystal structures and offer excellent semiconducting properties. Here, we report three novel OIMHs, (PPA)₆InBr₉ (PPA = [C₆H₅(CH₂)₃NH₃]⁺), (PBA)₂SbBr₅, and (PBA)₂SbI₆ (PBA = [C₆H₅(CH₂)₄NH₃]⁺), showing typical zero-dimensional (0D) structure, octahedra dimers, and corner-sharing one-dimensional chains and crystallized in the monoclinic system with P2₁, P2₁/c, and C2/c space groups, respectively. (PPA)₆InBr₉, (PBA)₂SbBr₅, and (PBA)₂SbI₆ have experimental optical band gaps of ∼3.16, ∼2.24, and 1.48 eV, respectively. (PPA)₆InBr₉ exhibits bright-orange light emission centered at 642 nm with a full-width at half-maximum of 179 nm (0.51 eV) and a Stokes shift of 277 nm (1.46 eV). After Sb³⁺ doping, the peak position did not change, and the photoluminescence quantum yield increased significantly from 9.2 to 53.0%. The efficient emission of Sb:(PPA)₆InBr₉ stems from the isolated ns² luminescent center and strong electron–phonon coupling, making the spin-forbidden ³P₁–¹S₀ observable. By combining commercial blue and green phosphors with orange-red-light-emitting (PPA)₆In_0.99Sb_0.01Br₉, a white-light-emitting diode was constructed, with the color-rendering index reaching up to 92.3. Our work highlights three novel 0D OIMHs, with chemical doping of Sb³⁺ shown to significantly enhance the luminescence properties, demonstrating their potential applications in solid-state lighting.

J. Mater. Chem. C, 2022,10, 9841-9848.https://doi.org/10.1039/D2TC01672A

As an emerging material, organic–inorganic metal halides (OIMHs) have been widely studied in the field of optoelectronics in recent years. In this work, a series of compounds (TMEDA)₃(Sb_xBi_1−x)₂Cl₁₂·H₂O (0.1 ≤ x ≤ 0.6) (TMEDA = N,N,N′-trimethylethylenediamine) were synthesized. The incorporation of Sb³⁺ greatly enhanced the photoluminescence quantum yield of (TMEDA)₃Bi₂Cl₁₂·H₂O from 1% to 38%. The variation in the degree of distortion of the inorganic octahedra and the relatively suitable distances between metal ions are considered to be the reasons for the intense emission. (TMEDA)₃(Sb_xBi_1−x)₂Cl₁₂·H₂O (0.1 ≤ x ≤ 0.6) exhibited a yellow phosphorescence emission at 605 nm and 595 nm under excitation at 305 nm and 375 nm, respectively. With the incorporation of Sb³⁺, changes in the emission intensity under different excitation wavelengths showed different trends. Thus, we attribute the yellow broadband emissions to the triplet emission of Bi³⁺ and Sb³⁺. Finally, we combined (TMEDA)₃(Sb_0.5Bi_0.5)₂Cl₁₂·H₂O with commercial phosphors and a near-ultraviolet light-emitting diode chip to prepare a white-light-emitting diode device, which exhibited a high color-rendering index of 94.4. The aim of our work was to investigate the structural effects of the photoluminescence of Sb³⁺-doped OIMHs and to further explore ways to improve the Sb³⁺ emission efficiency in the field of photoluminescence of OIMHs.

J. Mater. Chem. C, 2022,10, 13137-13142.https://doi.org/10.1039/D2TC02838G

Low-dimensional organic–inorganic metal halides with broad light emission have drawn widespread attention, however, the low thermal stability has been a major obstacle to their commercialization. Herein, zero-dimensional (C₉H₁₅N₃)ZnCl₄ with space group P2₁ was synthesized for the first time. (C₉H₁₅N₃)ZnCl₄ emits blue fluorescence at room temperature with external quantum efficiency as high as 42.5%, which are among the highest reported for Zn-based OIMHs, and it is comparable with the commercialized phosphors. Notably, the luminous integral intensity of (C₉H₁₅N₃)ZnCl₄ at 470 K remains more than 50% of that at room temperature. Mn²⁺ doping of (C₉H₁₅N₃)ZnCl₄ was conducted to improve the photoluminescence. With increasing Mn²⁺ concentration, the title compounds underwent fluorescence conversion from blue to green. The external quantum efficiencies of (C₉H₁₅N₃)ZnCl₄ : 5%Mn²⁺ and (C₉H₁₅N₃)ZnCl₄ : 50%Mn²⁺ were 43.7% and 42.9%, respectively. More importantly, (C₉H₁₅N₃)ZnCl₄ : 5%Mn²⁺ exhibited different luminous colors at different temperatures. As the temperature decreased from 290 to 110 K, the luminous color changed from green to light blue. Finally, a composite film was prepared to demonstrate the temperature response of this material, and the absolute sensitivity reaches 0.57%/K. These findings fill in the gaps for low-temperature indication and expand the application scenarios of OIMHs.

ACS Appl. Electron. Mater. 2022, 4, 4068−4076.https://doi.org/10.1021/acsaelm.2c00705

Phosphors with narrow-band emission are in great demand for liquid crystal display backlighting applications. In this work, four zero-dimensional Mn²⁺-based organic–inorganic metal halides (OIMHs), (C₁₃H₂₆N)₃MnBr₄·Br, (C₁₃H₂₆N)₂MnCl₄, and (C₇H₁₈N)₂MnX₄ (X = Cl, Br), were synthesized, and their crystal structures were solved. Under blue-light excitation, all of the materials exhibited bright narrow-band green luminescence centered at 515–525 nm with high photoluminescence quantum yields (PLQYs). Significantly, (C₁₃H₂₆N)₃MnBr₄·Br and (C₁₃H₂₆N)₂MnCl₄ exhibited small full width at half-maximum (FWHM) values of 43 and 48 nm with PLQYs of 77.8 and 79.3% at room temperature, respectively. Compared with the reported luminescent OIMHs, ultrahigh thermal quenching temperatures were observed, and at 420 K, emission intensities of (C₁₃H₂₆N)₃MnBr₄·Br and (C₁₃H₂₆N)₂MnCl₄, remained 82.7 and 64.2% of those at room temperature, respectively. The rigid environment provided by the C₁₃H₂₆N⁺ cation has a strong confinement effect on the [MnX₄]^2– tetrahedra, leading to a narrower FWHM and higher thermal quenching temperature. Finally, (C₁₃H₂₆N)₃MnBr₄·Br was combined with commercial phosphors to fabricate light-emitting diodes (LEDs) with a wide color gamut of up to 113% NTSC (National Television System Committee). This work provides a reference for designing the OIMHs for liquid crystal display LEDs by tuning the organic cations.