Natural resources conversion for optoelectronic materials application

• Main Authors: Chang, Tsung-Yuan, 張宗元
• Other Authors: Lin, Hsiu-Mei
• Format: Others
• Language: zh-TW
• Published: 2017
• Online Access: http://ndltd.ncl.edu.tw/handle/61391782683449693187

博士 === 國立臺灣海洋大學 === 光電科學研究所 === 105 === We have investigated on the converting natural resources into the optoelectronic materials. The research topics include: (1) Converting natural waste (shell) into the white-light phosphors. (2) Using chlorophyll extract from diatom algae as a anti-reflection layer on silicon solar cells. (3) Using GaN or Rh6G as gain media to couple with diatom frustules for the demonstration of random laser action. The first topic is the preparation of co-doping Eu2+, Mn2+ into a single-phased Ca9Gd(PO4)7 (CGP) white-light phosphors by conventional solid state reaction method. The sources of calcium which hosted in CGP:Eu2+,Mn2+ were transferred by biological shellfish (clams). The X-ray powder diffraction (XRD), photoluminescence excitation (PLE) and photoluminescence (PL) spectra were used to ensure the physical properties of CGP:Eu2+,Mn2+. The PL spectra by 350 nm excitation showed a broad blue-greenish emission band ranging from 375 nm to 650 nm, and the PLE spectra (λem = 490 nm) showed a broad hump from 250 to 450 nm. As the above results showed the Eu2+ could efficiently absorb near ultraviolet (300–400 nm) light and give blue to red broadband emissions. Therefore, Eu2+ can act as a sensitizer, transferring a part of its energy to activator ions, manganese ions (Mn2+). Finally, we successfully demonstrated the fabrication and packaging of a phosphor-converted white light-emitting diodes (pc-WLEDs) by pumping a white-emitting CGP: Eu2+, Mn2+ phosphor with an UV LED chip. For the second topic, chlorophyll (chl) was extracted from diatom with ethanol. Comparing with other solvents (such as actone and hexane), the use of ethanol was more safety and environmentally friendly. The spectra of chlorophyll extraction were well characterized by UV-vis spectrophotometer and PL techniques. In our measurements, we detected no PL emission for chlorophyll c (chl-c), which is likely due to its relatively weaker natural emission or much lower fraction in the sample as compared with chlorophyll a (chl-a). Thus, the monitored PL peak for the diatom extract can be attributed to chl-a content, which is determined spectroscopically to be about 100 mg L-1. Chl-a absorted the UV to blue (250–470 nm) light, than emitted red light (670 nm). From the above optical analysis, the primary active content (chl-a) is responsible for photon energy conversion in the diatom extract, which makes the diatom extract be an attractive candidate for violet-to-red photon conversion. We will demonstrated an approach to improve the Efficiency of silicon solar cells by incorporating the diatom extract as an layers of antireflection of light and photon energy conversion. Finally, we demonstrated a random laser actions in ultraviolet and visible regions based on the composites consisting of bio-derived diatom frustules. Owing to the low optical loss from porous network of diatom structures, the random laser actions were generated from GaN film or Rh6G dye via using biological diatoms as scattering centers. Interestingly, both ultraviolet and visible-range random laser actions with very sharp peaks can be easily obtained, indicating the size of diatom frustules can constitute the optical resonance conditions for generating random lasers.