Compact near‐infrared (NIR) light sources with broad emission band are essential to enable NIR spectroscopy compatible with portable devices, and phosphor‐converted light emitting diodes (pc‐LEDs) are efficient, low‐cost, and compact light sources. However, it is more challenging to develop highly efficient and thermally stable broadband NIR phosphors than conventional phosphors for white LEDs. Here, a series of solid solution phosphors with broadband NIR emission designed by cationic substitution in Cr3+ activated garnet Gd3Sc2Ga3O12 are reported. The internal quantum efficiency of Cr3+ emission can be significantly improved to nearly 100% via the substitution of ScO6 with smaller AlO6 octahedrons, which is attributed to the reduction of antisite defects. Moreover, the phosphor with optimized composition shows highly thermally stable emission, which renders the as‐fabricated pc‐LED with high‐power (750.8 mW) NIR emission covering the wavelength range of 700–1000 nm. The results could advance the development of NIR pc‐LEDs as high‐performance light sources for miniature NIR spectrometers.

Phosphor‐converted light‐emitting diodes (pc‐LEDs) with broadband near‐infrared (NIR) emission have emerged as compact light sources for portable NIR spectroscopy. However, the associated broadband NIR phosphors suffer from low quantum efficiency (QE) and severe thermal quenching. Here the realization of highly efficient (internal QE ≈ 90%) and nearly zero‐thermal‐quenching broad NIR emission in Cr3+ and Yb3+ codoped Gd3Sc1.5Al0.5Ga3O12 (GSGG) via efficient energy transfer from Cr3+ to Yb3+ is reported, whereby a high‐performance NIR pc‐LED is obtained that can generate ultra‐broad‐band NIR emission covering the whole range of 700−1100 nm with high output power (50 mW at a current of 100 mA) and high photoelectric efficiency (24% at a current of 10 mA). The results not only demonstrate that Cr3+ and Yb3+ codoped GSGG has great potential for compact NIR light sources, but also indicate that the strategy of energy transfer can be exploited for developing new NIR phosphors with both high QE and thermal stability.

a rapid development and now become the preferred white light sources for general illumination and backlight display. [1] Near-infrared (NIR) pc-LEDs were accordingly proposed as a new-generation light source to circumvent the limitations of the application of conventional counterparts like NIR semiconductor LEDs, supercontinuum lasers and halogen lamps to compact optical systems. [2] Especially, NIR pc-LEDs covering a wide spectral range of 700-1100 nm, when coupled with Si-based photodetectors, can miniaturize NIR spectroscopy to be an integrated module for mobile phones and smart wearables, thereby realizing instant identification of food, clothing and pharmaceuticals, and real-time monitoring of human health. [3] However, the spectral properties and optical output power of NIR pc-LEDs are still far from practical application for the lack of satisfactory NIR phosphors.Phosphors play a key role in the conversion of narrowband blue light from LED chips to the desired broadband NIR one. Over the past few years significant effort has been devoted to exploiting a variety of ions including Cr 3+ , [4][5][6][7] Mn 2+ , [8] and Eu 2+[9] as the broadband NIR emitters, but only Cr 3+ has hitherto exhibited high internal quantum efficiency (IQE) and good photoluminescence (PL) thermal stability in a handful of host crystals, such as Gd 3 Sc 1.

As the left neighbor of carbon in the periodic table, boron is very similar to carbon in electronic properties and strong bonding characters, and both undertake important roles in living organisms. [8][9][10][11] However, due to the unique trivalent electronic configuration, boron is among the most chemically versatile elements, which shows polymorphism in low-dimensional structures and thus richer properties, such as high-temperature superconductivity, high carrier mobility, massless Dirac fermions, superhardness, to name a few. [12][13][14][15][16][17][18][19][20][21] Although the 2D form borophene has recently been experimentally realized by several groups under ultrahigh-vacuum conditions and by another one with chemical vapor deposition (CVD), [12,15,22,23] the related researches of borophene are still mainly concentrated on theoretical predictions and computational calculations. [13,20,21,[24][25][26][27][28] Experimental work is largely lagged behind, which, to a large extent, is due to its chemical and structural complexities and thus challenging synthesis. [13,14] On the other hand, up to now, most of 2D boron-related researches are on the electronic and mechanical properties by theoretical methods, let alone experimental study of its optical properties and related applications. According to several recent theoretical predictions, 2D boron bears fascinating features that are totally different from other 2D materials, such as thicknessdependent transparency and visible/near-infrared plasmons. [26,27] Here, based on liquid-exfoliated boron nanosheets, for the first time, we demonstrate an all-optical phase shifter at the telecommunication band that is mediated by the efficient photo-thermal response in boron nanosheets. The constructed phase shifter shows an order of magnitude faster response speed and higher modulation efficiency compared with other 2D material-based similar devices. Consequently, a high-efficiency and stable allfiber, all-optical modulator was successfully realized based on a Mach-Zehnder interferometer (MZI) configuration, which could be further employed for all-optical logic gating operations. As proof-of-concept demonstrations, we successfully achieved all-optical logic AND and NOT gates by exploiting the superior photo-thermal response in boron nanosheets. Our work marks an important step toward exploring the optical and photonic applications of 2D boron nanosheets.Due to its unique trivalent electronic configuration, boron features richer properties as well as higher chemical and structural complexities compared with its right neighbor carbon. Consequently, over a decade later than the exfoliation of graphene, borophene has just been experimentally demonstrated on certain metal substrates and under ultrahigh-vacuum conditions, which, however, limit its wide and in-depth experimental researches. Here, for the first time, by employing liquid-exfoliated boron nanosheets, all-optical signal processing application is explored based on its superior photo-thermal response. A stable all-opt...

No abstract