【作者】 高翔；

【导师】 胡斌； 屠国力；

【作者基本信息】 华中科技大学 ， 光学工程， 2014， 博士

【摘要】 本论文探索出将氯原子引入到共轭聚合物主链的直接聚合方法,并将主链含有氯原子的共轭聚合物成功应用到聚合物发光二极管中；同时合成出侧链含有溴原子的共轭聚合物,探究了侧链溴原子对共轭聚合物光学性能、电化学性能的影响,并将其作为给体材料应用到有机/聚合物太阳能电池中。具体内容和主要结论概述如下：设计合成了2,3-双(3-正辛烷氧基苯基)-5,8-二溴-6,7-二氯喹喔啉,利用该分子中氯原子和溴原子在Stille反应中反应活性的差异,将其与2,5-双三甲基锡噻吩聚合,首次成功制备出主链含氯原子的、结构规整的给体-受体交替共聚物(PC1QT)。同时合成出其氟代(PFQT)、未取代(PQT)的结构相似的聚合物,以便系统研究氯原子对共轭聚合物性能的影响。尽管氯原子的电负性低于氟原子的电负性,但PC1QT比PFQT具有更深的LUMO能级。通过量子计算发现,与氟原子不同的是,氯原子扭曲了聚合物主链,使LUMO能级局域在受体单元中。这可能是PC1QT具有更低的LUMO能级的原因。而使用联噻吩双锡盐作为给体单元合成的含氯聚合物PC1Q2T,与PC1QT相比,具有相似的LUMO能级和较高的HOMO能级。说明含氯共轭聚合物的HOMO和LUMO能级可以独立调控。同时因为氯原子的位阻效应,这些含氯共轭聚合物的吸收光谱明显的蓝移,Stokes位移增大,自吸收减小。以2,3-双(3-正辛烷氧基苯基)-5,8-二溴-6,7-二氯喹喔啉为受体单元,调节给体单元中噻吩个数,合成出三种红光聚合物材料PC1Q2HT、PC1Q3T和PC1Q4T。将PC1Q2HT、 PC1Q3T和PC1Q4T作为客体材料,选用高效绿光材料F8BT为主体材料,制备聚合物发光二极管器件。以PC1Q3T为客体材料制备出了发光峰位于678nm,色坐标为(0.66,0.34),亮度接近2000cd m-2,外量子效率超过1%的深红光聚合物发光二极管。以PC1Q4T为客体材料制备出了发光峰位于692nm,色坐标为(0.67,0.32),亮度接近1500cd m-2的深红光聚合物发光二极管；发光峰位于708nm,色坐标为(0.69,0.31),亮度超过400cd m-2,外量子效率超过0.6%的近红外聚合物发光二极管。设计合成出4,7-二溴-5,6-二氯苯并[1,2,5]噻二唑,并以其为受体单元合成出共轭聚合物。由于该分子内氯原子和溴原子的反应活性在Stille反应中差异较小,无法作为单体直接用于聚合；但可以通过Suzuki聚合得到主链含氯原子的共轭聚合物。将氯原子引入到苯并噻二唑单元上,会使聚合物材料的LUMO能级升高。分析量子计算结果,推断造成氯原子在喹喔啉体系和苯并噻二唑体系中对能级调控作用差异的原因可能是喹喔啉和苯并噻二唑中吡嗪环和噻二唑环的电子能力和位阻存在差异。以4,7-二(5-溴-2-噻吩基)-5,6-二氯苯并[1,2,5]噻二唑为受体单元,以2,7-双频哪醇硼酸酯-芴为给体单元合成的聚合物PFC1DTBT作为客体材料以3%的浓度掺杂到主体绿光材料F8BT中,制备出器件结构为ITO/PEDOT:PSS(30nm)/F8BT:聚合物(100nm)/Ca (20nm)/Al(100nm)的聚合发光二极管器件,电致发光峰位于632nm处,色坐标为(0.60,0.40),亮度最大可以达到15580cd m-2,电流效率为1.2cd A-1,最大外量子效率为1.1%。将溴原子引入到给体材料的侧链,通过调节含溴单元的比例,合成出一系列给体材料。发现在溶液中,聚合物的摩尔吸光系数随着含溴比例的变化有先减小后增大的趋势,荧光光谱峰值随溴含量的增加而逐渐红移；薄膜状态时,随着含溴比例的增加,吸收光谱中的肩峰越发明显,但聚合物的荧光光谱基本相同。这是因为溴原子被极化后与材料间的偶极-偶极相互作用弱于聚合物链段间的偶极-偶极相互作用。溶液中聚合物链段间相互作用较弱,枝接在侧链的溴原子被极化后对材料的影响得以显现；但薄膜状态时,聚合物链段间相互作用占主导地位。同时溴原子引入的分子间弱相互作用,促进了材料的堆积,使吸收光谱中肩峰的强度随溴含量的提高而增强。更多还原

【Abstract】 In this dissertation, straight-forward synthitic rout has been developed to introduce chlorine atoms onto the backbone of conjugated polymers and these chlorine-bearing conjugated polymers can be used as light-emitting materials. Additionally, bromine atoms were attached at the end of the side-chain of conjugated polymers. The effects of bromine on the conjugated polymers have been well studied. The detailed results were briefly described as below:5,8-dibromo-6,7-dichloro-2,3-bis(3-(octyloxy)phenyl)quinoxaline was designed and synthesized. Copolymerizing with2,5-bistrimethyltinthiophen, regeoregular chlorine-bearing donor-acceptor alternating conjugated copolymer (PC1QT) was obtained for the first time by taking advantage of the different reactivies between chlorine and bromine in Still reaction. The fluoride (PFQT) and non-substitued (PQT) analogues were also synthesized to systemtically study the effects of chlorine atoms on the conjugated polymers. PC1QT exhibited deepest LUMO energy level although the electron affinity of chlorine is less than that of fluorine. The calculation based on density functional theory (DFT) proved that the chlorine atoms twisted the backbone of the copolymers causing localized LUMO and resulting deepest LUMO energy level. When2,2’-bithiophene was used as the donor moiety, the resulted copolymer PC1Q2T exhibited higher HOMO compared with that of PC1QT and maintained deep LUMO energy level indicating the HOMO and LUMO levels can be modified individually. These chlorine-bearing copolymers exhibited blue-shifted absorption spectra and large Stokes shift which can be attributed to the large steric hindrance of chlorine atoms.5,8-dibromo-6,7-dichloro-2,3-bis(3-(octyloxy)phenyl)quinoxaline was used as the acceptor moiety and oligomer thiophenes were used as the donor moieties, three red-emitting copolymers, PClQ2HT、PClQ3T and PClQ4T, were obtained by changing the number of thiophene. Efficient green-emitting F8BT was chosen as the host material to fabricate polymeric light-emitting diodes. When PClQ3T was used as the guest light emitting material, Deep red centered at678nm, CIE (0.66,0.34) with brightness about2000cd m-2and EQE above1%was obtained; When PClQ4T was used as the guest light emitting material, deep red to NIR emission centered at698nm with brightness about1500cd m-2and centered at708nm with brightness over400cd m-2with reasonable efficiency (0.21-0.69%) was obtained. All these results obtained with simple device structure ITO/PEDOT:PSS/light emitting layer/Ca/Al, indicating the chlorine-bearing copolymers are competitive deep red to NIR light-emitting materials.4,7-dibromo-5,6-dichlorobenzo[1,2,5]thiadiazole was synthesized and used as the acceptor moiety to synthesize conjugated polymers. In this molecule, the difference in reactivity between the chlorine atoms and the bromine atoms is too small to process Stille reaction but large enough to process Suzuki reaction to obtain regioregular chlorine-bearing polymers with high molecular weight. Higher LUMO levels of the final polymers were observed compared with non-chloride polymers. The calculation results based on DFT indicated different effects of chlorine atoms on polymers containing benzothiadizole and quinoxaline respectviely could be attributed to the differences in electron withdrawing ability and steric hindrance between the thiadizole of benzthiadizole and the pyrazine of quinoxaline. Efficient red-emitting polymer PFClDTBT was obtained when4,7-bis(5-bromothiophen-2-yl)-5,6-dichlorobenzo[c][1,2,5]thiadiazole was used as the acceptor moiety and fluorene was used as the donor moiety. The single-layer devices with the configuration of ITO/PEDOT:PSS/Polymer/Ca/Al exhibited saturated red emission at632nm with a luminous efficiency of1.2cd A-1with CIE (0.60,0.40) when the doping ratio was3%. The maximum brightness and external quantum efficiency (EQE) could reach15580cd m-2and1.1%respectively. A series of donor materials were obtained by finely tuning the content of bromine attached at the side-chain of conjugated polymers. Theses bromine atoms could affect the optical properties when the donor materials were dissolved in solvent, can not only change the absorption coefficiency but also make the fluorescence emission maxima red shift. When the materials were cast on quartz, the shoulder peak in absorption spectra became clearer but no change happened in the fluorescence spectra. This is because that the effect of polarized bromine atoms is weaker than the dipole-dipole interaction of segments. When the materials were dissolved, the effect of polarized bromine overwhelmed because the segments are far away from each other and caused changes in optical properties. But in, films, dipole-dipole interaction of segmetns is dominant resulting the same fluorescence spectra. Additionally, weak interaction might exist because of bromine atoms resulting clearer shoulder peak in the absorption spectra.更多还原