A high-performance blue filter was demonstrated and employed to increase the modulation bandwidth and dramatically reduce the bit error rate of a white-LED-based VLC system. It has a very wide stopband (500-1050 nm), high transmittance passband (average 97.5 percent in the blue signal range of 430-485 nm), and a sharp and precise cutoff edge. Not only can the blue filter completely remove the slow phosphorescent component from modulated signals, but it can also effectively reject ambient solar radiation. Meanwhile, the blue light signals of the LED can almost be retained. This results in a high SNR and improves the performance of a VLC system, including increased modulation bandwidth and reduced BER. The BER can be dramatically reduced from 3.6 × 10 ^-2 to 1.7 × 10 ^-4 at 50 MHz bandwidth, and from 2.6 × 10 ^-2 to 1.9 × 10 ^-5 at a distance of 30 cm compared to a VLC system without our blue filter. More importantly, the stop band covers the whole response range of the receiver except for the blue signal band, which strongly increases the ability of a VLC system used in the sun or outdoors.

High performance colored absorbers with a TiN _x O _y absorbing layer and a TiO ₂ /Si ₃ N ₄ /SiO ₂ dielectric stack are designed and fabricated for architecturally integrated solar energy applications.

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A simple new way to tune the optical phase transition temperature of VO ₂ films was proposed by only controlling the pressure of oxygen during the annealing process. Vanadium films were deposited on glass by a large-scale magnetron sputtering coating system and then annealed in appropriate oxygen atmosphere to form the VO ₂ films. The infrared transmission change (at 2400 nm) is as high as 58% for the VO ₂ thin film on the glass substrate, which is very good for tuning infrared radiation and energy saving as smart windows. The phase transition temperature of the films can be easily tuned from an intrinsic temperature to 44.7 °C and 40.2 °C on glass and sapphire by annealing oxygen pressure, respectively. The mechanism is: V ³⁺ ions form in the film when under anaerobic conditions, which can interrupt the V ⁴⁺ chain and reduce the phase transition temperature. The existence of V ³⁺ ions has been observed by x-ray photoelectron spectroscopy (XPS) experiments as proof.

Solar selective absorbers are the core part for solar thermal technologies such as solar water heaters, concentrated solar power, solar thermoelectric generators and solar thermophotovoltaics. Colorful solar selective absorber can provide new freedom and flexibility beyond energy performance, which will lead to wider utilization of solar technologies. In this work, we present a monolithic integration of colored solar absorber array with different colors on a single substrate based on a multilayered structure of Cu/TiN_xO_y/TiO₂/Si₃N₄/SiO₂. A colored solar absorber array with 16 color units is demonstrated experimentally by using combinatorial deposition technique via changing the thickness of SiO₂ layer. The solar absorptivity and thermal emissivity of all the color units is higher than 92% and lower than 5.5%, respectively. The colored solar selective absorber array can have colorful appearance and designable patterns while keeping high energy performance at the same time. It is a new candidate for a number of solar applications, especially for architecture integration and military camouflage.