We introduce white light generation using CdSe/ZnS core–shell nanocrystals of single, dual, triple and quadruple combinations hybridized with InGaN/GaN LEDs. Such hybridization of different nanocrystal combinations provides the ability to conveniently adjust white light parameters including the tristimulus coordinates (x,y), correlated colour temperature (Tc) and colour rending index (Ra). We present the design, growth, fabrication and characterization of our white hybrid nanocrystal-LEDs that incorporate combinations of (1) yellow nanocrystals (λPL = 580 nm) on a blue LED (λEL = 440 nm) with (x,y) = (0.37,0.25), Tc = 2692 K and Ra = 14.69; (2) cyan and red nanocrystals (λPL = 500 and 620 nm) on a blue LED (λEL = 440 nm) with (x,y) = (0.37,0.28), Tc = 3246 K and Ra = 19.65; (3) green, yellow and red nanocrystals (λPL = 540, 580 and 620 nm) on a blue LED (λEL = 452 nm) with (x,y) = (0.30,0.28), Tc = 7521 K and Ra = 40.95; and (4) cyan, green, yellow and red nanocrystals (λPL = 500, 540, 580 and 620 nm) on a blue LED (λEL = 452 nm) with (x,y) = (0.24,0.33), Tc = 11 171 K and Ra = 71.07. These hybrid white light sources hold promise for future lighting and display applications with their highly adjustable properties.

The authors present the design, growth, fabrication, experimental characterization, and theoretical analysis of blue quantum electroabsorption modulators that incorporate ϳ5 nm thick In 0.35 Ga 0.65 N / GaN quantum structures for operation between 420 and 430 nm. Growing on polar c plane on sapphire, they obtain quantum structures with zigzag potential profile due to alternating polarization fields and demonstrate that their optical absorption blueshifts with applied electric field, unlike the redshift of conventional quantum confined Stark effect. In InGaN / GaN quantum structures, they report the largest absorption change of 6000 cm −1 for 6 V bias swing around 424 nm, holding promise for blue optical clock generation and injection directly into silicon chips. © 2007 American Institute of Physics. ͓DOI: 10.1063/1.2424642͔ Today silicon microelectronics is limited in operating speed: the electrical interconnects suffer from the RC limitation; scaling does not mitigate this problem.1 This leads to a bottleneck in electrical clocking. Optical clocking is proposed as a remedy.2 Optical clock distribution is implemented commonly in the near infrared ͑IR͒ spectral region where optoelecronic devices are readily available.3,4 However, silicon photodetectors, for example, those fabricated in standard complementary metal-oxide-semiconductor ͑CMOS͒ process, unfavorably exhibit long absorption length and thus a diffusion tail problem in the near IR. This limits the operating speed of Si CMOS photodetectors to 1 Gbits/ s. 5 To circumvent this problem, one approach is to utilize high-speed III-V photodetectors hybrid integrated on Si chips. This, however, introduces difficulties related to post-CMOS fabrication. On the other hand, unlike in the IR, optical clock injection directly to Si is possible in the blue, where Si features a very short absorption length ͑ϳ100 nm at 400 nm͒ and thus lacks the diffusion tail. 6 However, there exists no chip-scale device to modulate optical clock signal in the blue at high speeds to date. In this letter, we propose blue InGaN / GaN based quantum electroabsorption modulators for a possible chip-scale solution in optical clock modulation in the blue. Here we present the design, epitaxial growth, fabrication, experimental characterization, and theoretical analysis of our quantum electroabsorption modulators that incorporate ϳ5 nm thick In 0.35 Ga 0.65 N / GaN quantum structures in a p-i-n diode architecture for operation in the blue spectral range, as shown in Fig. 1.We grow these quantum structures on the polar c plane of GaN on sapphire in metal organic chemical vapor deposition ͑MOCVD͒ and obtain a zigzag potential profile due to high polarization fields with alternating directions in their heterostructures. We study the electroabsorption behavior of these quantum zigzag structures for proof-of-concept demonstration of their use in blue modulation. In the blue range, using InGaN / GaN quantum structures, we experimentally demonstrate the largest optical absorption change of 6000 cm −1 wi...

Using first-principles density functional theory calculations, we systematically investigate the structural, electronic and vibrational properties of bulk and potential single-layer structures of perovskite-like CsPb 2 Br 5 crystal. It is found that while Cs atoms have no effect on the electronic structure, their presence is essential for the formation of stable CsPb 2 Br 5 crystals. Calculated vibrational spectra of the crystal reveal that not only the bulk form but also the single-layer forms of CsPb 2 Br 5 are dynamically stable. Predicted single-layer forms can exhibit either semiconducting or metallic character. Moreover, modification of the structural, electronic and magnetic properties of single-layer CsPb 2 Br 5 upon formation of vacancy defects is investigated. It is found that the formation of Br vacancy (i) has the lowest formation energy, (ii) significantly changes the electronic structure, and (iii) leads to ferromagnetic ground state in the single-layer CsPb 2 Br 5 . However, the formation of Pb and Cs vacancies leads to p-type doping of the single-layer structure. Results reported herein reveal that single-layer CsPb 2 Br 5 crystal is a novel stable perovskite with enhanced functionality and a promising candidate for nanodevice applications.

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The interest in all-inorganic halide perovskites has been increasing dramatically due to their high quantum yield, band gap tunability, and ease of fabrication in compositional and geometric diversity. In this study, we synthesized µm long and ~4 nm thick CsPbBr3 nanowires (NWs). They were, then, integrated into electrospun polyurethane (PU) fibers to examine polarization behavior of the composite fiber assembly. Aligned electrospun fibers containing CsPbBr3 nanowires show remarkable increase in degree of polarization from 0.17 to 0.30. This combination of NWs and PU fibers provides a promising composite material for various applications such as optoelectronic devices and solar cells.