染料敏化太陽能電池(Dye-Sensitized Solar Cells, DSCs)若使用不同顏色之染料為敏化劑，元件可呈現不同顏色，具多色彩性。染料吸附在TiO2時，須吸收藍光的互補光–橘光(590 nm ~ 620 nm)，且在藍光(450 nm ~ 495 nm)的吸收很弱，元件才能呈現深藍色。本實驗室先前合成以Benzothienoisoindigo (BTI)單元為輔助拉電子基的BTI-17，在DMSO中雖呈現藍色，但吸附在TiO2時呈現紅色，因最大吸收波長藍位移至綠光區域，且在藍光區域的吸收很強。本研究改以Indoline為推電子基，或將π-bridge由Benzene改為Furan，或以Indigo衍生物–diindolo[3,2,1-de:3′,2′,1′-ij][1,5]naphthyridine-6,13-dione (IND)為輔助拉電子基，合成BTI-19、BTI-21、INDT-1及INDT-2四個有機染料。在DMSO中，BTI-19、BTI-21呈現綠色，INDT-2呈現藍綠色，INDT-1呈現藍色。吸附在TiO2時，染料的最大吸收波長皆有大幅度的藍位移，因固著官能基去質子化所造成，且藍位移程度隨推電子基的推電子能力提高而增加。其中BTI-19、BTI-21分別因推電子基之推電子能力的強度增強或分子的平面性增加，成功使染料吸附在TiO2時的最大吸收波長在橘光區域，但對於紅光的吸收亦強、並在綠光區域吸收較弱，故呈現綠色。而含最強推電子基的BTI-19，有較好的前置軌域能階分布，並且LUMO能階與TiO2傳導帶能階間也有足夠的位能差，受光激發的電子有機會順利注入至TiO2的傳導帶。INDT-1及INDT-2吸附在TiO2時雖呈現藍紫色，但不同於BTI系列染料，其在藍光區域的吸收很弱，有機會經由分子的修飾，讓其吸附在TiO2上時呈現藍色。

The color of a Dye-sensitized Solar Cell (DSC) depends on the color of the sensitizer. To fabricate DSC exhibit blue color, the dye adsorbed on TiO2 should show blue color. In other words, dye adsorbed on TiO2 must absorb the orange light (590 nm ~ 620 nm, complementary color of blue light) and the absorption in blue light range (450 nm ~ 495 nm) should be weak. BTI-17, which was synthesized previously by our group containing the Benzothioneisoindigo (BTI) unit as an auxiliary acceptor moiety, is blue color in DMSO but turns red when adsorbed on TiO2, due to the λmax blue-shifted to the green region (554 nm) and the absorption in the blue region is strong. In this research, Indoline was used as donor unit, or Benzene was replaced by Furan to be the π-bridge, or using the Indigo derivative: diindolo[3,2,1-de:3′,2′,1′-ij][1,5]naphthyridine-6,13-dione (IND) as an auxiliary acceptor unit, resulting in BTI-19, BTI-21, INDT-1 and INDT-2 four new organic dyes, to modify the structure of BTI-17. In DMSO, BTI-19 and BTI-21 were green, INDT-2 was blue-green, INDT-1 was blue. When the dyes adsorbed on TiO2, the λmax of all four dyes has a large blue-shift, which is caused by the deprotonation of the anchoring group of the dye molecule. The degree of the blue-shift increases with the increasing in the electron-donating ability of the donor. Among them, BTI-19 and BTI-21 with stronger electron-donating ability of the donor or higher planarity of the molecule, the λmax of the dye adsorbed on TiO2 is in the orange region. Nevertheless, it also absorbs the red light and the absorption in the green region is weak but strong im blue region, therefore displays green color. The BTI-19 dye with the strongest donor has a proper frontier-orbital distribution, and the LUMO energy level is high enough to assure the electron injetction to TiO2 conduction band edge could be a good organic dye for DSC. INDT-1 and INDT-2 although are blue-purple color when adsorbed on TiO2, however their absorption in the blue region is weak, providing a chance to modify the strudture to present blue color when adsorbed on TiO2.

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