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Power conversion efficiency (PCE) and stability of tin perovskite solar cells (TPSCs) are major concerns in developing lead‐free photovoltaics. Photovoltaic performance of TPSCs often suffers from the oxidation of Sn2+, organic degradation, and ion migration, which inevitably cause plenty of trap states and render inferior device parameters. Herein, a natural ascorbic acid is first introduced for high‐performance TPSCs as a multifunctional reductant to suppress the oxidation of Sn2+ and regulate trap states accordingly. Interestingly, it is found that the ascorbic acid reduces Sn4+ to Sn2+ by CC double bonds and forms a complex with Cs0.05FA0.95SnI3 perovskites via strong hydrogen bonding interactions. By virtue of theoretical calculations, the mechanism of the ascorbic acid role is further clarified. Apart from effective passivation and suppressing trap density, a superoxide interaction between perovskite and ascorbic acid is proposed. The existence of ascorbic acid successfully improved the energy barrier for O2− generation. As a result, a significantly improved PCE from 8.95% to 13.32% is achieved for Cs0.05FA0.95SnI3 TPSCs with 0.5% ascorbic acid incorporation under AM 1.5 G illumination. In addition, our devices maintain 90% value of initial PCE after 500 h storage. [ABSTRACT FROM AUTHOR]

The lagging development of deep‐blue perovskite light‐emitting diodes (PeLEDs) heavily impedes their practical applications in full‐color display due to the absence of spectrally stable emitters and the mismatch of carrier injection capacity. Herein, we report highly efficient deep‐blue PeLEDs through a new chemical strategy that addresses the dilemma for simultaneously constant electroluminescence (EL) spectra and high‐purify phase in reduced‐dimensional perovskites. The success lies in the control of adsorption‐energy differences between phenylbutylamine (PBA) and ethylamine (EA) interacting with perovskites, which facilitates narrow n‐value distribution. This approach leads to an increased exciton binding energy and enhanced surface potential, hence improving radiative recombination. As a result, an external quantum efficiency of 4.62 % is achieved in PeLEDs with a stable EL peak at 457 nm, demonstrating the best reported result for deep‐blue PeLEDs so far. [ABSTRACT FROM AUTHOR]

Quasi‐2D perovskite‐based light‐emitting diodes (Q‐2D PeLEDs) have recently gained attention as promising technology for future lighting and displays, due to their remarkable advancements in device efficiency. In order to make Q‐2D PeLEDs technology practical in display and lighting applications, it is essential to ensure a long lifespan, particularly at large area and high brightness levels. In this work, the top‐down crystallization mechanism of the Q‐2D perovskite films is explored through introducing alkali metal Na+ to precisely control the phase distribution in the vertical space. Furthermore, the robust interactions between Na+ and PbBr64− octahedra increases the lifetime of the device by orders of magnitude via passivating the halogen vacancies on the perovskite surface as well as replacing insulating ligands, reducing Joule heat. Eventually, the operating half‐lifetime (T50) of small area device (0.04 cm2) exceeds 612 h and even when the effective area is expanded ≈56 times (2.25 cm2), the T50 remains impressively high at 115 h. Additionally, these devices exhibit excellent external quantum efficiency (EQE) reaches 26.5% and 19.2%, respectively. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) organic–inorganic halide perovskite materials have favorable stability and unique photoelectric properties in comparison with three-dimensional (3D) counterparts and have become a new topic in the field of materials. However, the environmental toxicity of lead is still a major obstacle to their commercialization. In this regard, 2D lead-free halide perovskites come into being and will be the main concern for future commercial applications. Here, we first introduce the synthesis strategies, crystal structure and basic optoelectronic properties of 2D lead-free halide perovskite materials. Subsequently, the application status of solar cells and light-emitting diodes in recent years is summarized. Finally, the existing problems and future development prospects of these kinds of materials are discussed, which provide a reference for the design and preparation of high-performance 2D lead-free halide perovskite optoelectronic devices. [ABSTRACT FROM AUTHOR]

A two-step synthetic route using RE(OH)CO3 colloid spheres as the sacrificial template was designed to prepare monodisperse, pure bastnasite (RECO3F: RE = Ce, La, Pr, Nd) with a hole structure for the first time. A variety of morphologies, including jujube core-like, stacked nanoblocks, and stacked nanosheets were obtained through changing the ratio of reactants. The phase, structure, shapes, and photoluminescence properties of samples were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and photoluminescence (PL) spectroscopy. The CeCO3F:Ln3+ (Ln = Tb, Eu, Dy) phosphors give green, yellow and blue emission, respectively, due to the f–f transitions of Ln3+ ions. Furthermore, the energy transfer from Ce3+ to Dy3+ and Tb3+ was described in detail. [ABSTRACT FROM AUTHOR]

Ln3+-Doped fluorides are economical and highly efficient luminescent materials, which play a crucial role in LEDs, biolabeling, and sensors. Therefore, Na5Gd9F32:Ln3+ sub-microspheres with tunable multicolor emissions were successfully synthesized via a simple water bath method employing colloidal Gd(OH)CO3 spheres as precursors. Samples were characterized by XRD, SEM, TEM, EDS and PL. It was found that the hydrolysis of BF4− ions had a dynamic effect on the retention of the morphology of the product owing to the mild reaction environment caused by the low hydrolysis rate of BF4− ions. Upon excitation by ultraviolet light, the Na5Gd9F32:Ln3+ (Ln = Eu, Tb, Dy, Sm, Ho) phosphors underwent characteristic f–f transitions and gave rise to red, green, green, yellow, and pale green emissions, respectively. Moreover, various emission colors could be obtained by using different excitation wavelengths and adjusting the Eu3+/Tb3+ molar ratio owing to energy transfer between Tb3+ and Eu3+ ions in the Na5Gd9F32 host. The energy transfer mechanism was demonstrated to be a dipole–dipole interaction. The multicolor luminescent phosphors with a certain dopant concentration based on a single host and excitation wavelength may have potential applications in the field of lighting displays. [ABSTRACT FROM AUTHOR]

In this study, a class of vernier yttrium oxyfluoride (Y5O4F7 denoted as V-YOF) with a variety of shapes and sizes was formed by adjusting the crystal growth environment; after calcination, the samples can maintain the morphology of the precursor; this may be attributed to the topotactic chemical transformation. A comparison of the fluorescence results shows that the hexagonally shaped microcrystal strips can effectively improve the light-emitting characteristics; further, to explore the growth mechanism of precursors, time-dependent experiments and three-dimensional growth simulations have been carried out. They suggest that the formation of hexagonal strips may be due to the unique way that the crystals grow from the interior space to the outer wall. Moreover, Tm3+/Dy3+-codoped V-YOF phosphors exhibit excellent white light emission (CIE: x = 0.338, y = 0.313 close to that of standard white light (0.33, 0.33)) due to energy transfer. These results confirm that the V-YOF phosphors may have potential applications in the field of luminescent materials. [ABSTRACT FROM AUTHOR]

In this study, monodisperse and uniform β-NaYF4 hexagonal microtubes were successfully synthesized via a simple hydrothermal method without any organic surfactants, employing Y(OH)CO3 colloid spheres as precursors. The possible formation mechanism was studied on the basis of a series of time-dependent control experiments and its intrinsic crystal structure. The integrated emission intensity of β-NaYF4:0.05Tb3+ is almost 1.78 times stronger than that of α-NaYF4:0.05Tb3+. In addition, the photoluminescence properties of β-NaYF4:Ln3+ (Ln = Eu, Tb, Tm, Sm, Ho) were studied in detail, and it was found that the photoluminescence color of β-NaYF4:0.03Tm3+ phosphor was close to the standard blue light (0.14, 0.08). Moreover, by co-doping the Tb3+ and Eu3+ ions into the β-NaYF4 host, multicolor tunable emissions were obtained due to the efficient energy transfer from Tb3+ to Eu3+ at 368 nm excitation. These merits demonstrate that this material may find potential application in color display fields. [ABSTRACT FROM AUTHOR]

Three-dimensional (3D) flower-like CeO 2 /BiOI heterostructures with different Ce/Bi molar ratio were successfully synthesized via a hydrothermal method using polyvinylpyrrolidone (PVP) as surfactant. The X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM) results indicate that the CeO 2 nanoparticles were successfully loaded on the surface of the flower-like BiOI. The photodegradation experiment demonstrated that the photocatalytic efficiency of CeO 2 /BiOI samples were higher than that of pure BiOI and CeO 2 , and CeO 2 /BiOI heterostructure showed the best photocatalytic performance when the amount of CeO 2 located at BiOI up to 15%. The result also exhibits that CeO 2 /BiOI catalysts possess higher photocatalytic efficiency for Rhodamine B (RhB) and methylene orange (MO) degradation, while it has a slight influence for phenol elimination. Meanwhile, the repeated photocatalytic degradation of RhB experiment reveals excellent photostability. A possible mechanism of photocatalysis was also explored and proposed. Furthermore, loading CeO 2 on the surface of BiOI can accelerate the separation rate of photogenerated electron-hole pairs, which is analyzed by photoluminescence (PL) spectroscopy, photocurrent experiments (PC) and electrochemical impedance spectroscopy (EIS). These results exhibit that BiOI can be modified by CeO 2 and there exists synergistic effect between CeO 2 and BiOI. The present work provides a new means to synthesize heterostructured photocatalyst for environmental remediation. [ABSTRACT FROM AUTHOR]

Perovskite single-crystal films are promising candidates for high-performance perovskite optoelectronic devices due to their optoelectrical properties. However, there are few reports of single-crystal films of tin based perovskites. Here, for the first time, we realize the controllable growth and preparation of lead-free tin perovskite MASnI 3 single crystals via inverse temperature crystallization (ITC) strategy with γ-butyrolactone (GBL) as solvent. The solubility characteristics of MASnI 3 in GBL are clarified by quantitative analytical method. Highly repeatability experiments are further demonstrated using this unique solubility and ITC properties. Sequentially, using space limiting method, tin perovskite MASnI 3 single-crystal thin films are fabricated with micron-scale thickness, which is highly desired for efficient tin perovskite solar cells. Our MASnI 3 single-crystal thin films show typical single-crystalline features including strongly optical absorbance with sharp absorption edges, pure-phase x-ray diffraction patterns, and absence of Sn(IV) x-ray photoelectron spectroscopy. We believe that our findings will further broaden the application prospects of tin perovskite MASnI 3 single crystals and cause a new upsurge in exploring the field of lead-free perovskite single-crystal growth., (© 2022 IOP Publishing Ltd.)

A two-step synthetic route using RE(OH)CO3 colloid spheres as the sacrificial template was designed to prepare monodisperse, pure bastnasite (RECO3F: RE = Ce, La, Pr, Nd) with a hole structure for the first time. A variety of morphologies, including jujube core-like, stacked nanoblocks, and stacked nanosheets were obtained through changing the ratio of reactants. The phase, structure, shapes, and photoluminescence properties of samples were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and photoluminescence (PL) spectroscopy. The CeCO3F:Ln3+ (Ln = Tb, Eu, Dy) phosphors give green, yellow and blue emission, respectively, due to the f-f transitions of Ln3+ ions. Furthermore, the energy transfer from Ce3+ to Dy3+ and Tb3+ was described in detail.

Ln3+-Doped fluorides are economical and highly efficient luminescent materials, which play a crucial role in LEDs, biolabeling, and sensors. Therefore, Na5Gd9F32:Ln3+ sub-microspheres with tunable multicolor emissions were successfully synthesized via a simple water bath method employing colloidal Gd(OH)CO3 spheres as precursors. Samples were characterized by XRD, SEM, TEM, EDS and PL. It was found that the hydrolysis of BF4- ions had a dynamic effect on the retention of the morphology of the product owing to the mild reaction environment caused by the low hydrolysis rate of BF4- ions. Upon excitation by ultraviolet light, the Na5Gd9F32:Ln3+ (Ln = Eu, Tb, Dy, Sm, Ho) phosphors underwent characteristic f-f transitions and gave rise to red, green, green, yellow, and pale green emissions, respectively. Moreover, various emission colors could be obtained by using different excitation wavelengths and adjusting the Eu3+/Tb3+ molar ratio owing to energy transfer between Tb3+ and Eu3+ ions in the Na5Gd9F32 host. The energy transfer mechanism was demonstrated to be a dipole-dipole interaction. The multicolor luminescent phosphors with a certain dopant concentration based on a single host and excitation wavelength may have potential applications in the field of lighting displays.

In this study, monodisperse and uniform β-NaYF 4 hexagonal microtubes were successfully synthesized via a simple hydrothermal method without any organic surfactants, employing Y(OH)CO 3 colloid spheres as precursors. The possible formation mechanism was studied on the basis of a series of time-dependent control experiments and its intrinsic crystal structure. The integrated emission intensity of β-NaYF 4 :0.05Tb 3+ is almost 1.78 times stronger than that of α-NaYF 4 :0.05Tb 3+ . In addition, the photoluminescence properties of β-NaYF 4 :Ln 3+ (Ln = Eu, Tb, Tm, Sm, Ho) were studied in detail, and it was found that the photoluminescence color of β-NaYF 4 :0.03Tm 3+ phosphor was close to the standard blue light (0.14, 0.08). Moreover, by co-doping the Tb 3+ and Eu 3+ ions into the β-NaYF 4 host, multicolor tunable emissions were obtained due to the efficient energy transfer from Tb 3+ to Eu 3+ at 368 nm excitation. These merits demonstrate that this material may find potential application in color display fields.