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PHOTOACOUSTIC AND PHOTOELECTROCHEMICAL CHARACTERIZATION OF TiO2 PHOTONIC CRYSTAL SENSITIZED WITH CdSe QUANTUM DOTS

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修士論文の英文要旨

大学院 電気通信学研究科 博士前期課程 量子·物質工学専攻

氏名

Diguna Lina Jaya 学籍番号 0433030

論文題目

Photoacoustic and Photoelectrochemical Characterization of

TiO

2

Photonic Crystal Sensitized with CdSe Quantum Dots

Inverse opal TiO2 supposes to surpass the efficiency of conventional TiO2 solar cell due to its

large interconnected pores, which enables better penetration of dye sensitizers. Indeed, it also exhibits photonic band gap that may cause a significant change in dye absorbance by adjusting the position of photonic band gap to the position of dye absorption. Semiconductor quantum dots (QDs) have attracted attention as dye substitute due to its quantum confinement effect. TiO2 photonic crystal has been successfully fabricated by a simple method wherein the voids

in the artificial opal latex are filled with nanosized TiO2 by dropping TiCl4 into the latex

matrix, hydrolyzing and heating at 80 OC for 10 min This filling process is repeated three times and finally calcination of the template and annealing of TiO2 were conducted at 450

O

C. The resulted TiO2 photonic crystal was then sensitized with CdSe QDs by chemical deposition for

various times. The optical absorption and the incident photon to current conversion efficiency (IPCE) properties were characterized using photoacoustic (PA) and photoelectrochemical methods.

The red shift of the PA spectra can be clearly seen with increasing deposition time. The optical absorption shoulders in PA spectra of CdSe deposited samples show blue shift relative to the band gap energy of 1.73 eV for bulk CdSe indicating the occurrence of quantum confinement effect in CdSe particles. Increase in IPCE value and clear shift to visible region are observed with the increasing deposition times, indicating photosensitization of CdSe QDs. All CdSe sensitized samples show two peaks at ∼ 3.0 and 2.2 eV. The peak at ∼3.0 eV may indicate the enhancement of light absorption due to photonic band gap. On the other hand, the peak at 2.2 eV corresponds to the first excitation of CdSe QDs. Recently, it was found that increasing deposition temperature may cause fast growth and rapid deposition of CdSe QDs.

1 . 5 2 . 0 2 . 5 3 . 0 3 . 5 4 . 0 4 . 5 0 . 0 0 . 2 0 . 4 0 . 6 0 . 8 1 . 0 1 . 2 Wavelength (nm) CdSe deposition time (h) 0 8 2 12 4 24 N o rm . PA Int en si ty (A rb . U ni ts )

Photon energy (eV) 8 0 0 7 0 0 6 0 0 5 0 0 4 0 0 3 0 0 1 . 5 2 . 0 2 . 5 3 . 0 3 . 5 4 . 0 4 . 5 0 1 0 2 0 3 0 4 0 Wavelength (nm) CdSe deposition time (h) 24 12 8 4 2 0 IPC E ( % )

Photon Energy (eV)

8 0 0 7 0 0 6 0 0 5 0 0 4 0 0 3 0 0

Fig. 3 Normalized PA spectra of the TiO2 photonic

crystal for different CdSe deposition times.

Fig. 4 IPCE spectra of the TiO2 photonic crystal

参照

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