White light-emitting diodes (WLEDs) have matched the emission efficiency of florescent lights and will rapidly spread as light source for homes and offices in the next 5 to 10 years. WLEDs provide a light element having a semiconductor light emitting layer (blue or near-ultraviolet (nUV) LEDs) and photoluminescence phosphors. These solid-state LED lamps, rather than organic light emitting diode (OLED) or polymer light-emitting diode (PLED), have a number of advantages over conventional incandescent bulbs and halogen lamps, such as high efficiency to convert electrical energy into light, reliability and long operating lifetime. To meet with the further requirement of high color rendering index, warm light with low color temperature, high thermal stability and higher energy efficiency for WLEDs, new phosphors that can absorb excitation energy from blue or nUV LEDs and generate visible emissions efficiently are desired. The criteria of choosing the best phosphors, for blue (450−480 nm) and nUV (380−400 nm) LEDs, strongly depends on the absorption and emission of the phosphors. Moreover, the balance of light between the emission from blue-nUV LEDs and the emissions from phosphors (such as yellow from Y3Al5O12:Ce3+) is important to obtain white light with proper color rendering index and color temperature. Here, we will review the status of phosphors for LEDs and prospect the future development.

Comparing to the traditional CdS buffer layer, zinc magnesium oxide (ZMO) offers the following advantages for CdTe-based thin-film solar cells: it introduces a spike to conduction band offset, which reduces interface recombination that is beneficial for increasing open-circuit voltage (V OC) and decreases parasitic optical absorption of the buffer layer that is favorable for enhancing short-circuit current (J SC). However, ZMO/CdTe thin-film solar cells often show the so-called S-kink behavior in their current–voltage curves, making it difficult to reproduce the expected benefits. Here, we show that S-kink can be successfully eliminated, and improved V OC and J SC can be simultaneously achieved if the CdCl2 treatment process is conducted in oxygen-free atmosphere. As a result, the device efficiencies increased from 9.2% to 16.1%. Our device characterizations and simulations reveal that a sufficiently high electron density of the ZMO buffer layer is critical to eliminate the S-kink, which is achievable through an oxygen-free CdCl2 treatment.

The first borate carbonate UV nonlinear optical material Pb7O(OH)3(CO3)3(BO3) was hydrothermally synthesized, which features a (3,9)-connected IrSi3-like structure constructed by Pb7O(OH)3(BO3) units and carbonates. This compound exhibits a large second-harmonic generation (SHG) response about 4.5 times that of KH2PO4 (KDP), attributed to synergistic interactions between the stereoeffect of the Pb(II) cations and coparallel BO3 and CO3 triangles groups.

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Hydrazine hydrate was employed to prevent Fe agglomeration and sulphate ions were used as the S source, which together led to Fe/N/S-CNTs with high performance.

Instead of developing a novel red phosphor individually, this work proposes the production of white light by combining a near-ultraviolet/ultraviolet diode chip with blue and special yellow phosphors: the yellow phosphor includes the red and green components with high color saturation. The availability of this scheme is demonstrated by preparing a white light-emitting diode (WLED) with color rendering index (Ra) up to 90.3. The desired single-mass yellow phosphor is successfully screened out from the YVO(4):Bi(3+),Eu(3+) system by using a combinatorial chemistry approach. When the emission color and luminous efficiency are both considered, the best composition for producing white light is (Y(1-s-t)Bi(s)Eu(t))VO(4) with 0.040 < or = s < or = 0.050 and 0 < t < or = 0.015. The red component that is required for a high-Ra WLED is obtained through sensitizing luminescence of Eu(3+) by Bi(3+) in a YVO(4) host; meanwhile, both Bi(3+) and Eu(3+) emission are improved by keeping the Bi(3+) and Eu(3+) contents close to the critical concentration.

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