應用於有機太陽能電池新型碳六十/七十衍生物之設計與開發

Abstract

本計劃施行的重點在於以製備高效率有機薄膜太陽能電池為方向, 合成與探討具 有thiophene, selenophene, 及 tellurphene 新式碳六十/碳七十衍生物與具有開口 的碳六十衍生物的物理化學性質, 以期作為新型太陽能電池薄膜材料。此計劃之實行主 要可分為兩階段, 第一階段為碳六十衍生物設計、合成、鑑定、及電化學性質的探討。 由於分子的加成位置會影響聚合後巨分子骨架型式及元件的構像, 因此探討不同數目 的加成單元及異構物對有機元件的影響相當重要。碳六十衍生物所要探討的分子為碳六 十的單一加成, 含thiophene、selenophene、tellurphene 的衍生物基體, 其次為探討 碳六十的雙重加成物, 此階段須分離不同位置加成的單體, 再其次為探討碳六十的三 重加成物, 具有, 主要探討 C3 與 D3 衍生物的聚合物性質為主。其次, 將合成碳六十 衍生物的研究模式, 運用於碳七十衍生物的探討, 涵蓋合成具有thiophene, selenophene, 及tellurphene 的衍生物基體及其性質探討。第二階段為以碳六十為基 體, 將碳六十加成為帶有數個異端偶合基在trans-1 相關位置的衍生物, 再將所加成的 分子偶合, 形成內包碳六十的巨分子, 以利於合成雙層的分子萵苣 (double-shelled fullerene nano-onions) 。 第三階段將進行設計合成具有推拉電子基的碳六十衍生物 應用於太陽能電池材料的探討。我們將仰賴溶液相及固相(HSVM)的反應模式。例如, 將 aryl amines, thiophene, selenophene, phthalimide 以化學反應置放於C60 分子上, 將此材料製成有機元件並做I-V (電流-電壓) 及 IPCE (incident photon to current efficiency) 性能測試。第四階段將進行合成具有開口的碳六十衍生物並探討其有機元 件特性。 此計劃之實行將依賴電腦計算資源, 以AM1、PM3、B3LYP/3-21g、 及 B3lyp/6-31g* 為理論基礎, 以優化 (optimization) 探討並設計具高對稱性的碳六十/碳七十衍生物, 並以 B3LYP/6-31G** 來計算比較所遷涉到分子群的單點能量(single point energy), 並解決所設計分子在合成時涉及的反應機構問題。 根據計算分析結果, 合成鑑定所設 計的分子並製備有機薄膜以量測其效益。 在此階段, 分子的光譜鑑定亦須仰賴計算光 譜 (NMR 化學位移) 作初部的結構推論。 由於以碳六十/碳七十衍生物為材料的有機薄 膜太陽能電池效益與分子的結構與還原電位息息相關, 以理論計算估計分子的bandgap 亦是相當重要的一環。 因此, 此計劃將以計算為輔來完成, 達到高效率有機薄膜太陽 能電池的目的, 以解決未來能源的問題.

Conversion of solar energy to power is one of the most expected approaches that could substitute current energy-providing system. Despite the development of solar energy cell using inorganic silicons have progressed to commercialization, a goal to produce flexible cells using environment friendly organic materials with higher efficiency remains a barrier toward marketing. Wudl and Heeger et al serendipitously discovered that power could be generated from an organic thin film fabricated from materials of blending fullerene C60 and electron-donating polymers. Their discovery initiated continuing researches toward higher efficiencies using derivatized C60 molecules and various conducting polymers. Up to date, efficiency as high as 6.5 % has been recorded by Heeger et al. Despite that numerous examples have been reported with efficiencies of few percents using fullerene C60 derivatives, their fullerene [60] derivatives seem to use similar classes of compounds through direct functionalizations of C60 so that power conversion efficiency remains within that range. Our approach toward solar cell with much higher efficiency will rely on dramatic modifications of fullerene materials that will cast significant changes on electronic properties. Our designed C60 derivatives consist of semimetallic (Se) and metallic elements (Te) on C60/C70 derivatives, synthesis of doubled-shelled fullerenes and chalcogenophene-containing double-shell fullerenes, new hybrids of donor-acceptor system that contains aryl amines, phthalimide, benzothiofuran, and metals as significant moieties in fullerene derivatives. In a more detailed description of the synthetic portions, we will investigate functionalizations of fullerenes with selenium and tellurium-containing moieties and study their electronic properties by electrochemical methods. The researched derivatives include adducts with mono-, bis- and tris-additions. Separation of these resulting isomeric adducts will be conducted with high-pressure liquid chromatography and isomers will be characterized through spectroscopic methods (1H NMR, 13C NMR, HMQC, HMBC, MALDI-TOF, UV-vis, IR, and X-ray diffraction if necessary). Next, stepwise synthesis toward double-shell fullerenes will be studied. This will be started from couplings of addends on derivatized trans-1 fullerenes. We propose two approaches to the synthesis of trans-1 functionalized fullerenes with radiating pending moieties containing halogenated pyrene or benzopyrenes. Intramolecular electrocyclization or pyrolysis is a key step toward a double-shell fullerene. Once upon the double-shell fullerene structures have been obtained, we will soon investigate thiophene-, selenophene- and tellurphene-containing compounds of double-shelled fullerenes and their resulting regiochemistry, and particularly electrochemical and spectroscopic properties. The other approach would be taking advantages of molecular scaffolds of buckyferrocenes to the synthesis of carbon nano-onions precursors. A η6- metal complex with arenes on the two opposite poles of C60 will be the targets of our synthesis. Similar electrocyclization or pyrolysis will be carried out for the synthesis of nano-onions as described above. Last, we will synthesize open-cage fullerenes with large orifice through merging two small openings on C60 cage and fabricate into organic thin-film devices. To assist our synthetic progress, we will also use computations to search the most stable structures and aid characterizations throughout our projects. The optimizations of investigated molecules will essentially be taken at AM1, PM3, B3LYP/3-21G and B3LYP/6-31G* level of theories and their single point energies at B3LYP/6-31G** level. Other properties that will be studied through computations include frequency, NMR (1H and 13C), UV-vis, HOMO and LUMO energy levels.Because our initial project is mainly associated with design, synthesis, and electronic properties investigations, device fabrications will be soon addressed once synthetic targets become available in the near future.