【作者】 胡小链；

【导师】 陈红征； 施敏敏；

【作者基本信息】 浙江大学 ， 高分子材料， 2013， 博士

【摘要】 聚合物太阳电池因其具有质轻、廉价、柔性、可大面积溶液加工等优点引起了各国科学家的广泛关注。尽管近十年来聚合物太阳电池领域取得了重大的进展,离实际的商业化应用还是有较大的距离。理想的有机活性层材料,包括电子给体聚合物和电子受体,需要满足很多的性能要求,如宽吸收、高载流子迁移率、匹配很好的能级结构、给/受体间很好的相容性以及低廉的制造成本。目前为止富勒烯衍生物是聚合物太阳电池中性能最好的电子受体材料。但是它们也有一些自身的弱点,比如制备成本很高、能级调控困难、在可见光区及近红外区的吸收十分弱。一些窄带隙的D-A聚合物显示出了比被研究最多的聚3-己基噻吩(P3HT)更优越的光伏性能,如俞陆平等开发的聚(苯并双噻吩-alt-噻吩并[3,4-b]噻吩)(PTB)体系。但是几乎所有性能优越的D-A聚合物的合成路线十分繁冗,高的制造成本不利于进一步的商业化应用。基于上述这些考虑,在本论文中,我们设计合成了一系列的新型电子给/受体聚合物材料,它们的合成路线均较简易。我们对聚合物的化学结构、热稳定性、吸收特性、HOMO/LUMO能级结构以及光伏性能进行了详细的讨论。聚合物显示出较宽的吸收光谱、较优的能级结构以及较好的光伏性能。主要工作如下：1.通过2,7-咔唑与芳香酰亚胺单元的交替共聚合成了一系列新型窄带隙共轭聚合物。芳香酰亚胺单元包括萘酰亚胺、苝酰亚胺以及它们的二噻吩取代物。通过循环伏安法,表明这些聚合物是典型的n型半导体,它们的LUMO能级高于常用的[6,6]-苯基-C61-丁酸甲酯(PCBM)。以这些聚合物为电子受体,与电子给体P3HT复合制备了全聚合物太阳电池器件,其中基于2,7-咔唑与二噻吩苝酰亚胺的共聚物PCDTPDI的光伏性能最佳。基于P3HT:PCDTPDI的电池器件的光电转换效率为0.68%。2.考虑到在聚合物的侧链上引入吸电官能团可以有效降低聚合物的HOMO能级,以合成十分简易的3-酯基噻吩作为缺电单元,分别与富电单元联噻吩、苯并双噻吩共聚得到了两个新型酯基修饰的聚噻吩衍生物,PCTDT和PCTBDT。聚合物的吸收特性类似P3HT,但是HOMO能级相比P3HT降低很多。以聚合物为电子给体,与电子受体PCBM复合制备聚合物太阳电池器件。其中基于PCTBDT:PCBM的电池器件的光电转换效率为4.03%,开路电压达0.80V。3.通过将合成简易的3,4-二酯基噻吩以无规共聚的形式引入到聚合物中,合成了三个新型酯基修饰的聚噻吩并[3,4-b]噻吩衍生物(P1-P3)。聚合物的光学带隙为1.23～1.42eV。随着聚合物中3,4-二酯基噻吩含量的不断增加,聚合物的HOMO能级不断下降。以聚合物为电子给体,与电子受体PCBM复合初步制备了聚合物太阳电池器件。其中P1的光伏性能最佳,器件的光电转换效率为1.02%,基于P3:PCBM的电池器件可以获得0.71V的开路电压。4.通过将3,4-二酯基噻吩引入到含吡咯并吡咯烷酮(DPP)基团的聚合物中,合成了两个新型酯基修饰的含DPP基团的窄带隙共轭聚合物,无规的PCTDPP和规整的PDCTDPP.聚合物具有小于1.40eV的光学带隙及较低的HOMO能级。以聚合物为电子给体,与电子受体PCBM复合制备了聚合物太阳电池器件。其中基于PCTDPP:PCBM的电池器件的光电转换效率为3.52%,基于PDCTDPP:PCBM的电池器件的开路电压高达0.84V。5.通过Stille偶联反应合成了基于双噻吩吡咯(DTP)和噻吩酰亚胺(TPD)的交替共聚物PDTPTPD.由于引入了吸电性的TPD单元,聚合物具有较窄的光学带隙(1.62eV)及较低的HOMO能级(-5.09eV)。以聚合物为电子给体,与电子受体PCBM复合初步制备了聚合物太阳电池器件。基于PDTPTPD:PCBM的电池器件的光电转换效率为1.9%,开路电压可达0.74V。6.通过在聚合物主体中同时引入强弱两种吸电基团,合成得到了一系列基于吡咯并吡咯烷酮(DPP)的-(D-A1-D-A2)n型的聚合物P4～P10。所有聚合物均具有窄的光学带隙(1.27～1.48eV)与低的HOMO能级(-5.25～-5.44eV)。以聚合物为电子给体,与电子受体PCBM复合初步制备了聚合物太阳电池器件。电池器件均具有较高的开路电压(Voc=0.72-0.91V),其中P8的光伏性能最佳,器件的光电转换效率为1.33%。此外,我们发现-(D-A1-D-A2)n这种分子设计可以有效获得高性能的双极性场效应晶体管,其中P7的电子与空穴迁移率相当平衡,均高达1.0cm2/V/s左右。更多还原

【Abstract】 Polymer solar cells (PSCs) have recently attracted considerable attention due to their advantages of low cost, light weight, flexibility, and facile large-area solution processability. Though impressive progresses have been made in this field over the past ten years, it is still far away from the industrial commercialization. The ideal active layer materials including the electron donor polymer and the electron acceptor should meet the requirements such as broad absorption, high carrier mobility, well matched energy levels, good compatibility with each other and low production cost. To date, fullerene derivatives are the most successful electron acceptors in PSCs. However, they still have many drawbacks such as high production cost, difficulty to tune the energy levels and poor absorption in the visible-to-near-infrared ranges. The photovoltaic performances of a few low band-gap donor-acceptor (D-A) polymers have exceed that of the most used poly(3-hexythiophene)(P3HT), such as the poly(benzodithiophene-alt-thieno[3,4-b]thiophene)(PTB) series discovered by L.P. Yu. However, the synthetic routes toward almost all excellent D-A polymers are very complicated which is not beneficial for industrial commercialization. With the above considerations in mind, in this dissertation, we designed and synthesized a series of new electron donor/acceptor polymers through few reaction steps. The chemical structure, thermal stability, optical absorption, HOMO/LUMO energy levels and photovoltaic properties of obtained polymers were studied. The polymers showed broad absorption, optimized energy levels and good photovoltaic performances. The works are listed as follows:1. A series of low band-gap conjugated polymers based on2,7-carbazole and arylene diimides (naphthalene diimide NDI and perylene diimide PDI) or dithienyl-arylene diimides were synthesized via Suzuki cross-coupling reaction. Through cyclic voltammetry measuremnts, it was found that all copolymers were n-type materials and their LUMO energy levels were higher than that of [6,6]-phenyl-C61butyric acid methyl ester (PCBM). Photovoltaic properties of the copolymers blended with P3HT as electron donor were investigated. Among four copolymers, the copolymer PCDTPDI alternating2,7-carbazole and dithienyl-perylene diimide exhibited the best photovoltaic performance with a power conversion efficiency (PCE) of0.68%.2. Considering that the HOMO energy level could be efficiently reduced by introducing the electron-accepting groups into the polymer side chain, the easily synthesized thiophene-3-carboxylate (CT) was chosen as the electron deficient units to copolymerize with electron-rich units like bithiophene (DT) and benzodithiophene (BDT). Thus, two new ester group functionalized polythiophene derivatives, PCTDT and PCTBDT, were obtained. The copolymers exhibited broad and strong absorptions in the visible region, which was similar to that of P3HT. Both copolymers showed lower HOMO energy levels than P3HT. Photovoltaic properties of the copolymers blended with PCBM as electron acceptor were investigated. PSC made from PCTBDT:PCBM blend showed a PCE up to4.03%with an open circuit voltage (Voc) of0.78V, a short circuit current (Isc) of8.19mA/cm2, a fill factor (FF) of63.2%.3. Three random ester-functionalized polythieno[3,4-b]thiophene derivatives (P1-P3) were synthesized by incorporating different contents of thiophene-3,4-dicarboxylate moiety into the polymer backbone. The copolymers exhibited low optical band gaps of1.23-1.42eV. The HOMO energy levels of the copolymers gradually decreased with increasing the content of the thiophene-3,4-dicarboxylate moiety. Preliminary photovoltaic properties of the copolymers blended with PCBM as electron acceptor were investigated. Among the three copolymers, PI exhibited the best photovoltaic performance with a PCE of1.02%and a Voc up to0.71V was achieved in the solar cell based on P3:PCBM blend.4. Two new ester-functionalized diketopyrrolopyrrole (DPP) containing polymers (random PCTDPP and regular PDCTDPP) were synthesized by incorporating thiophene-3,4-dicarboxylate moiety into the polymer backbone. The copolymers exhibited low optical band gaps below1.40eV and relatively low HOMO energy levels. Photovoltaic properties of the copolymers blended with PCBM as electron acceptor were investigated. PSC made from PCTDPP:PCBM blend showed a PCE of3.52%and a Voc up to0.84V was achieved in the solar cell based on PDCTDPP:PCBM blend.5. A new conjugated polymer (PDTPTPD) alternating dithienopyrrole (DTP) and thienopyrroledione (TPD) units was synthesized by Stille coupling reaction. The resulting copolymer showed both a low optical band gap of1.62eV and a low HOMO energy level of-5.09eV owing to the electronegativity of TPD moiety. Preliminary photovoltaic properties of the copolymers blended with PCBM as electron acceptor were investigated. PSC made from PDTPTPD:PCBM blend shows a PCE of1.9%and a Voc up to0.74V could be achieved.6. A series of-(D-A1-D-A2)n-type diketopyrrolopyrrole (DPP) containing polymers P4-P10were synthesized by incorporating both strong and weak electron-accepting units into the polymer backbone. The resulting copolymers exhibited both low optical band gap of1.27-1.48eV and deep HOMO energy levels of-5.25～-5.44eV. Preliminary photovoltaic properties of the copolymers blended with PCBM as electron acceptor were investigated. All photovoltaic devices featured high Voc (0.72-0.91V) and P8exhibited the best photovoltaic performance with a PCE of1.33%. Furthermore, we found the above molecule design is an efficient strategy to obtain high performance ambipolar field-effect transistors. P7showed quite balanced and high hole and electron field-effect mobilities with both around1.0cm2/V/s.更多还原