The amount of electric power for photovoltaic power generation depends on the location of the power plant and the direction of solar cell. The solar cell controls the generation of solar power plants. Therefore, the structure of solar cell, manufacturing method, and optic technology were factors contributing to increased solar cell efficiency; however, the technical limit has been reached. Herein, we propose a new method to increase the solar cell efficiency using a wavelength conversion technology that converts ultraviolet and infrared rays, which are not effectively used in solar cells, into effective wavelength of solar cell. We used fluoride Na(Ca)YF₄ phosphor for wavelength conversion. Then, a wavelength-conversion fluorescent paste, prepared using an organic-silicon binder, was used to prepare a film that was applied to Si solar cells. It was confirmed that conversion efficiency improved by 5% or more.

The white light of a hybrid LED is obtained by using red and green organic fluorescent layers made of polymethylmethacrylate (PMMA) films, which function as color down-conversion layers of blue light-emitting diodes. In this research, we studied the fluorescence properties of a red organic fluorophore, employing perylene bisimide derivatives applicable to hybrid LEDs. The solubility, thermal stability, and luminous efficiency are important characteristics of organic fluorophores for use in hybrid LEDs. The perylene fluorescent compounds (1A and 1B) were prepared by the reaction of 4-bromophenol and 4-iodophenol with N,N`-bis(4-bromo-2,6-diisopropylphenyl)-1, 6,7,12-tetrachloroperylene-3,4,9,10-tetracarboxyl diimide (1) in the presence of dimethyl formaldehyde (DMF) at 70℃. The synthesized derivatives were characterized by using 1H-NMR, FT-IR, UV/Vis absorption and PL spectra, and TGA analysis. Compounds 1A and 1B showed absorption and emission at 570 nm and 604 nm in the UV/Vis spectrum. We also documented favorable solubility and thermal stability characteristics of the perylene fluorophores in our work. Perylene fluorophore 1, with the 4-bromophenol substituent 1A, exhibited particularly good thermal stability and solubility in organic solvents.

We studied white organic light-emitting diodes using blue fluorescent and red phosphorescent materials.White single OLEDs were fabricated using SH-1 : BD-2 (3 vol.%) and CBP : Ir(mphmq)2(acac) (2 vol.%) as emitting layer (EML). The white single OLED using SH-1 : BD-2 (3 vol.% 8 nm) / CBP : Ir(mphmq)2(acac) (2vol.% 22 nm) as emitting layer showed maximum current efficiency of 8.8 cd/A, Commission Internationale del``Eclairage (CIE) coordinates of (0.403, 0.351) at 1,000 cd/㎡, and variation of CIE coordinates with (0.402 ±0.012, 0.35 ± 0.002) from 500 to 3,000 cd/㎡. The white tandem OLED using SH-1 : BD-2 (3 vol.% 12 nm) /CBP : Ir(mphmq)2(acac) (2 vol.% 18 nm) showed maximum efficiency of 19.6 cd/A, CIE coordinates of (0.354,0.365) at 1,000 cd/㎡, and variation of CIE coordinates with (0.356 ± 0.016, 0.364 ± 0.002) from 500 to 3,000 cd/㎡. Maximum current efficiency of the white tandem OLED was more twice as high as the single OLED. Our findings suggest that tandem OLED was possible to produce improved efficiency and excellent color stability.

In order to develop a LED luminaire for naval-submarines which can replace a conventional one with two-compact fluorescent lamp (CFL) of 18 W, we analyzed the electrical and optical performance of the conventional luminaire. A LED luminaire was fabricated as compact as possible based on the analyzed data. The weight of the prototype LED luminaire is 1.8 kg, reducing up to 58% of the conventional one. The use of LED package for the submarine luminaire could reduce the power consumption from 38 W to 14.5 W with the same optical performance. The reason is that the optical efficacy of the LED luminaire improved by 2.47 times as 61.9 lm/W, compared to 25.1 lm/W for the conventional one.

Based on both organic synthesis and theoretical calculations on the effects of molecular orbital energy levels of amines on the of fluorescence properties of the fluorophore, fluorescent "turn-on" chemosensors detecting hazardous substances, including aldehyde chemicals and Hg2 ion, were developed.