以碳、氮、矽原子及乙烯基為共價橋樑所形成之七與五環熔合多電子平面分子：合成、鑑定及其共軛高分子於有機太陽能電池與有機場效電晶體之應用

Abstract

在本論文中，我們將雙噻吩咔唑 (dithienocarbazole) 外圍噻吩的3號位置和中心咔唑的3與6號位置利用碳、氮、矽原子以及乙烯基為共價橋樑形成七環熔合多電子分子 (dithienocyclopenta-carbazole (DTCC)，dithienopyrrolo-carbazole (DTPC)， dithienosilolo-carbazole (DTSC) 與 dithienobenzo-carbazole (DTBC))，為了改善薄膜態下分子間的作用力，DTCC 的苯環側鏈被更具有柔軟性的正辛烷所取代而形成dithienocyclopenta-carbazole (DTCC-C8)，此外，以中心為芴 (fluorene) 的dithienocyclopenta-fluorene (DTCF) 也使用類似的方式來合成，在多環單體的合成上，以碳原子為價橋之 DTCC、DTCC-C8 與 DTCF 的關鍵合成步驟為 Friedel-Craft反應，而以乙烯基為價橋的DTBC 則主要是利用一步驟的多重Suzuki-Miyaura cross-coupling 來合成，另一方面，以矽與氮原子為價橋之 DTSC 與 DTPC 的關鍵合成步驟分別為 lithiation/nucleophilic addition 與一步驟的多重鈀催化 Buchwald–Hartwig 反應，此後，將這些新穎的多電子單體與缺電子受體 (benzothiadiazole (BT) 或 dithienylbenzothiadiazole (DTBT)) 一起共聚成新的給體-受體交錯型共軛高分子。 相較於非熔合高分子 poly(2,7-fluorene-alt-dithienylbenzothiadiazole) (PFDTBT) 與 poly(2,7-carbazole-alt-dithienylbenzothiadiazole) (PCDTBT)，含有階梯狀平面分子 DTCF與 DTCC 之 poly(dithienocyclopenta-fluorene-alt-benzothiadiazole) (PDTCFBT) 與poly(dithienocyclopenta-carbazole-alt-benzothiadiazole) (PDTCCBT) 表現出較紅位移的光學吸收與較窄的光學能隙，將材料依照此結構ITO/PEDOT:PSS/polymer:PC71BM/Ca/Al 製作成太陽能電池元件後，PDTCCBT 有較高的光電轉換效率3.7%，此外，修飾過側鏈的 DTCC-C8 其高分子 poly(dithienocyclopenta-carbazole-alt-benzothiadiazole) PDTCCBT-C8 表現出較強的分子間堆疊，因此其光學吸收較為紅位移，並且在元件方面也表現出較佳的效率 4.6% (開路電壓 0.74 V，短路電流 10.3 mA/cm2，填充因子 60.0%)，另一方面，由於在 DTSC 單體中的噻咯 (silole) 擁有拉電子的能力，所以導致了高分子 poly(dithienosilolo-carbazole-alt-benzothiadiazole) (PDTSCBT) 擁有較低的 HOMO 能階，反之，DTPC 擁有推電子能力的吡咯 (pyrrole)，其高分子poly(dithienopyrrolo-carbazole-alt-benzothiadiazole) (PDTPCBT) 的HOMO 能階則相對較高，而其光學能隙之大小順序為：PDTSCBT (1.83 eV) > PDTCCBT-C8 (1.64 eV) > PDTPCBT (1.50 eV)，這樣結果顯示出七環熔合多電子單體之推電子能力強弱為DTPC > DTCC-C8 > DTSC，太陽能電池元件方面，PDTSCBT 表現出最佳的光電轉換效率5.2%，並且擁有相當大的開路電壓0.82 V，我們也將單體 DTBC 與dithienylbenzothiadiazole 共聚成交錯型共軛高分子poly(dithienobenzo-carbazole-alt-dithienylbenzothiadiazole) (PDTBCDTBT)，其元件表現出相當高的5.5% 效率 (開路電壓 0.79V，短路電流 10.87 mA/cm2，填充因子 64.5%)，藉由將三氧化鉬 (molybdenum oxide，MoO3) 當做緩衝層，元件效率可以進一步的改進為6.2% (開路電壓 0.79V，短路電流 11.52 mA/cm2，填充因子 68.2%)，在五環熔合多電子單體方面，單一異構物且呈 angular 形狀的 anthradithiophene (aADT) 也被合成出來，此後，再與ditheniodiketopyrrolopyrrole 和 bithiophene 做共聚分別形成高分子poly(anthradithiophene-alt-dithienyldiketopyrrolopyrrole) (PaADTDPP) 與 poly(anthradithiophene-alt-bithiophene) (PaADTT)，有結晶性的 PaADTT 表現出高的電洞遷移率 (7.9 × 10-2 cm2V-1s-1) 與開關比 (1.1 × 107)，而以 PaADTDPP 為材料的太陽能電池元件則有3.66%的轉換效率，藉由添加添加劑1-chloronaphthalene (CN)，可以將效率更進一步的提升到4.24%，此光電轉換效率則是在以含有 anthradithiophene 的高分子之太陽能電池中最高效率的一個，最後，由於我們合成的多環單體都具有共平面且剛硬的特性，因此是相當適合用來製作成有機場效電晶體，PDTSCBT、PDTCCBT-C8 與PaADTDPP 分別表現出高的電洞遷移率0.073、0.110 與 0.073 cm2 V-1s-1。

In this research, the 3-positions of the two outer thiophenes of dithienocarbazole unit are covalently fastened to the 3,6-positions of the central 2,7-carbazole cores by carbon, nitrogen, silicon and ethylene bridges, leading to a new class of multifused heptacyclic units dithienocyclopenta-carbazole (DTCC), dithienopyrrolo-carbazole (DTPC), dithienosilolo-carbazole (DTSC) and dithienobenzo-carbazole (DTBC), respectively. To improve the intermolecular interactions in solid state, the original 4-octoxyphenyl side chains on the DTCC unit are replaced with the more flexible octyl groups to furnish a dithienocyclopenta-carbazole (DTCC-C8) unit. Structurally analogous to DTCC, carbon-bridged dithienocyclopenta-fluorene (DTCF) has also been synthesized but using fluorene as the central core. Friedel-Craft cyclization is the key step for the synthesis of carbon-bridged DTCC, DTCC-C8 and DTCF units, while a one-pot benzannulation via multiple Suzuki-coupling is utilized to efficiently synthesize ethylene-bridge DTBC. Silicon-bridge DTSC and nitrogen-bridged DTPC units were also successfully constructed by lithiation/nucleophilic addition and one-pot double palladium-catalyzed amination via Buchwald–Hartwig reaction, respectively. These newly designed electron-rich monomers were copolymerized with benzothiadiazole (BT) or dithienylbenzothiadiazole (DTBT) units to afford a range of new donor-acceptor alternating copolymers. Compared to nonfused poly(2,7-fluorene-alt-dithienylbenzothiadiazole) (PFDTBT) and poly(2,7-carbazole-alt-dithienylbenzothiadiazole) (PCDTBT), poly(dithienocyclopenta-fluorene-alt-benzothiadiazole) (PDTCFBT) and poly(dithienocyclopenta-carbazole-alt-benzothiadiazole) (PDTCCBT) containing ladder-type heptacyclic structures (DTCF and DTCC) with forced planarity exhibited red-shift absorption spectra and narrow band gaps. By fabricating conventional device with ITO/PEDOT:PSS/polymer:PC71BM/Ca/Al configuration, PDTCCBT exhibit a higher power conversion efficiency of 3.7%. Due to the side chains modification of DTCC-C8 unit to induce stronger interchain interactions, poly(dithienocyclopenta-carbazole-alt-benzothiadiazole) PDTCCBT-C8 exhibited more red-shift absorption and higher efficiency of 4.6% (Voc = 0.74 V，Jsc = 10.3 mA/cm2，FF = 60.0%) than PDTCCBT. On the other hand, the silole units in DTSC possess electron-accepting ability that lowers the highest occupied molecular orbital (HOMO) energy levels of poly(dithienosilolo-carbazole-alt-benzothiadiazole) (PDTSCBT), whereas stronger electron-donating ability of the pyrrole moiety in DTPC increases the HOMO energy levels of poly(dithienopyrrolo-carbazole-alt-benzothiadiazole) (PDTPCBT). The optical band gaps are in the following order: PDTSCBT (1.83 eV) > PDTCCBT-C8 (1.64 eV) > PDTPCBT (1.50 eV). This result indicates that the donor strength of the heptacyclic arenes is in the order: DTPC > DTCC-C8 > DTSC. The bulk heterojunction photovoltaic device using PDTSCBT as the p-type material delivered a promising efficiency of 5.2% with an enhanced Voc of 0.82 V. For DTBC, the photovoltaic device based on the poly(dithienobenzo-carbazole-alt-dithienylbenzothiadiazole) (PDTBCDTBT) possessing highly rigid and coplanar structure exhibited an PCE of 5.50% (Voc of 0.79 V, a Jsc of 10.87 mA/cm2, a FF of 64.5%). By using MoO3 as a buffer layer, the performance of the device was further improved to a high PCE of 6.2% with a Voc of 0.79 V, a Jsc of 11.52 mA/cm2, a FF of 68.2%. For the pentacyclic arene, an isomerically pure anti-anthradithiophene (aADT) arranged in an angular shape was developed. This newly designed 2,8-stannylated aADT monomer is copolymerized with a ditheniodiketopyrrolopyrrole unit and a bithiophene unit, respectively, to furnish poly(anthradithiophene-alt-dithienyldiketopyrrolopyrrole) (PaADTDPP) and thiophene-rich poly(anthradithiophene-alt-bithiophene) (PaADTT). PaADTT with crystalline nature achieve a high FET mobility of 7.9 × 10-2 cm2V-1s-1 with an on-off ratio of 1.1 × 107. The photovoltaic device based on the PaADTDPP exhibit a PCE of 3.66%. By adding 1.5 vol.% 1-chloronaphthalene (CN) as a processing additive, the PCE can be improved to 4.24%. The efficiency is the best one among these devices based on the polymers containing anthradithiophene. Finally, in view of the coplanar geometries and rigid structures of these ladder-type arenes, it is highly desirable to utilize these polymers for organic field-effect transistors (OFETs). PDTSCBT, PDTCCBT-C8 and PaADTDPP exhibited the high hole mobilities 0.073, 0.110 and 0.073 cm2 V-1s-1, respectively.