以原位溶膠-凝膠方法製備新型聚烷基噻吩-二氧化鈦混成材料及其性質探討。

Abstract

用於製備有機太陽能電池之光作用層材料中，聚噻吩（polythiophene）及二氧化鈦（titanium dioxide），由於其適當的電子能階及優良的電荷傳導能力，而常分別被使用為良好的電子供體及電子接受體。然而，直接將兩種材料進行物理性摻合，將常導致嚴重的相分離現象，使得聚噻吩經光激發而生成的激子，未能產生良好的電荷轉移，而降低了元件的能量轉換效率。 本研究中，我們首先合成2,5-dibromo-3-(6-bromohexyl)thiophene和2,5-dibromo-3-hexylthiophene兩種不同的單體，接著利用兩種單體以1比4莫爾比的進料量，再配合 Grignard metathesis 法成功地聚合出單體比例為1:4莫爾比的新型共聚物poly[3-(6-bromohexyl)thiophene-co-3-hexylthiophene]，之後利用強鹼t-BuOK，針對共聚物上溴官能基進行脫去反應，將溴官能基完全的轉換為雙鍵基團，接著我們再利用聚合物上的雙鍵官能基與triethoxysilane上之矽，在催化劑H2PtCl6的催化下進行反應，成功地將矽氧烷基團鍵結在高規則度聚噻吩上。接著，在改變不同相對溼度的實驗環境下，利用一個新的與簡單的原位溶膠-凝膠反應（in-situ sol-gel）方法，製備兩種有機/無機奈米混成材料( hybrid materials)－分別為poly(3-hexylhtiophene)與二氧化鈦及poly[3-(6-bromohexyl)thiophene-co-3-hexylthiophene]與二氧化鈦，並且藉由控制 TiO2前驅物之進料量，製備了多種不同TiO2固含量的混成材料。另外，我們以1H-NMR鑑定合成材料的結構，使用凝膠滲透層析儀(GPC)得到聚合物之平均分子量，再以SEM及AFM觀測兩種有機/無機奈米混成材料之表面特性。從SEM與AFM觀察到相對於P3HT與TiO2奈米混成材料，新型聚噻吩與TiO2奈米混成材料的相分離現象有大幅的降低。接著，利用UV與PL分析此兩種材料的光學性質，再以積分球分析比較此兩種材料的內部結構經過光照後產生的量子效率。

Polythiophene and titania are frequently used as good electron donor and electron acceptor in organic solar cells, respectively, due to their adequate energy levels and excellent charge transport properties. However, the compatibility between organic and inorganic materials is poor, thus usually leading to serious macro-scale phase separation upon blending. The main purpose of this thesis is to synthesize a hybrid material with minor phase separation. In this thesis, both 2,5-dibromo-3-(6-bromohexyl)thiophene and 2,5-dibromo-3-hexylthiophene were first synthesized and employed as monomers to prepare poly[3-(6-bromohexyl)thiophene-co-3-hexylthiophene] with 1:4 monomers ratios via Grignard metathesis. The terminal bromine groups in copolymers were transferred to double bonds by the elimination reaction using t-BuOK as reagent. Then poly[3-(6-triethoxysilyl)thiophene-co-3-hexylthiophene] were synthesized by treating the alkene-containing copolymers with triethoxysilane in the presence of H2PtCl6 catalyst. Chemical structures and molecular weight characteristics of monomers and polymers as-prepared were analyzed by 1H-NMR and GPC. Then, under different relative humidity conditions, poly(3-hexylthiophene/TiO2 and poly[3-(6-triethoxysilyl)thiophene-co-3-hexylthiophene]/TiO2 bulk heterojunction hybrid materials were prepared by in-situ sol-gel reaction with varying amount of titanium(IV) isopropaoxide in dried chloroform. From SEM and AFM analysis, the phase separation of novel poly(3-alkylthiophene)/TiO2 nano-hybrid materials is reduced as compared to the poly(3-hexylthiophene)/TiO2 hybrid materials. Then, the photophysical properties of both hybrid materials were analyzed by using UV and PL. The integrating sphere is used to analysis and comparing both hybrid material quantum yields after excitation at specific wavelength.