基于苯并二噻吩及苯并三噻吩的光伏材料合成和性能研究

发布时间：2018-05-15 10:39

本文选题：聚合物太阳能电池 + 苯并二噻吩衍生物　；参考：《湘潭大学》2017年博士论文

【摘要】：本论文简单的介绍了本体异质结(BHJ)型聚合物太阳能电池(PSCs)的光电转换工作原理及性能影响因素。着重综述了BHJ PSCs光敏活性层中的以苯并[1,2-b:4,5-b′]二噻吩(BDT)为代表单元的聚合物电子给体材料以及以傒二酰亚胺(PDI)为代表的小分子电子受体材料的研究进展及设计策略。在BHJ PSCs器件结构中,光敏活性层中材料的吸收光子能力、分子能级、溶解性、聚集态、光活性层形貌和载流子迁移率等都会对器件的光电转换效率(PCE)产生重要影响。为此,本论文从调控光敏活性层中材料的吸收光谱、HOMO/LUMO能级、溶解性、共混微相分离结构和载流子迁移率等方面出发,设计并合成了一系列基于BDT为推电子结构单元的新型聚合物给体材料以及以PDI为拉电子结构单元的受体小分子,并利用飞行时间质谱、核磁共振氢谱(碳谱)、元素分析以及高分辨质谱等检测手段对所合成的目标分子及聚合物进行了表征。同时,采用热重分析(TGA)、差示扫描量热法(DSC)、紫外-可见吸收光谱(UV-Vis)、循环伏安法(CV)、广角X射线衍射(WAXRD)、原子力显微镜(AFM)等分析方法表征了所合成的共轭聚合物给体材料及小分子受体材料的热性能、结晶性、光物理性质、电化学性能以及共混薄膜表面形貌。同时研究了以目标共轭聚合物为电子给体材料或以目标受体小分子为受体材料的BHJ PSCs器件的光电能量转换性能。本论文的主要研究内容如下:1.设计并合成了两种基于苯并[1,2-b:4,5-b′]二噻吩(BDT)为推电子结构单元(D),苯并[c][1,2,5]噻二唑为弱拉电子结构单元(A1),吡咯并[3,4-c]吡咯二酮(DPP)或异靛(ID)为强拉电子结构单元(A2)的有规三元共轭聚合物(D-A1-D-A2)PTer-DPP和PTer-ID。并详细地研究了A2拉电子结构单元的种类对有规三元共轭聚合物的光物理性质、电化学性能以及光电能量转换的影响规律。研究结果表明:PTer-ID在短波区域(300-550 nm)的吸收强于PTer-DPP;聚合物PTer-ID具有比PTer-DPP更小的π-π堆积距离,PTer-ID共混膜具有比PTer-DPP共混膜更高的空穴迁移率,故其PSC器件表现出更高的Jsc(10.01 mA cm-2);同时,PTer-ID的HOMO能级更低,故其PSC器件表现出更高的Voc(0.89V);因此,在未另外加入任何添加剂及优化处理条件下,基于聚合物PTer-ID的BHJ PSCs光伏器件PCE值为3.27%。而相同条件下基于PTer-DPP的器件PCE值仅为2.28%。2.以噻吩并[3,2-b]噻吩单元取代噻吩单元,设计并合成了两种噻吩并[3,2-b]噻吩单元分别在主链和侧链,且拉电子结构单元在共轭侧链的D-A型共轭聚合物PTT-DTBT和PT-DTTBT。并且详细地研究了噻吩并[3,2-b]噻吩单元在聚合物主链或共轭侧链的位置差异对聚合物的热性能、光物理性质、电化学性能以及器件光电转换性能的影响。研究结果表明,相比于噻吩并[3,2-b]噻吩单元在主链的聚合物PTT-DTBT,噻吩并[3,2-b]噻吩单元位于共轭侧链的聚合物PT-DTTBT具有更宽更红移的吸收光谱、更小的光学带隙、更高的空穴迁移率以及更好的薄膜共混性。在未加入任何添加剂及后处理条件下,基于聚合物PTT-DTBT/PC61BM和PT-DTTBT/PC61BM的BHJ PSCs器件效率分别为3.05%(Voc=0.82 V,Jsc=8.10 mA cm-2,FF=46%)和4.07%(Voc=0.79 V,Jsc=9.99 mA cm-2,FF=51%)。3.设计并合成了以4-硫烷基苯(SB)作为二维(2D)共轭侧链取代的BDT衍生物为推电子结构单元,并将其分别与4,7-二溴-5,6-二氟苯并[c][1,2,5]噻二唑(DFBT),4,7-(双(5-溴-4-己基)-2-噻吩基)5,6-二氟苯并[c][1,2,5]噻二唑(DTDFBT)和2-乙基己基-4,6-二溴-3-氟噻吩并[3,4-b]噻吩-2-甲酸酯(FTT)进行Stille偶联聚合,得到三种D-A型共轭聚合物PSB-DFBT,PSB-DTDFBT和PSB-FTT。并详细地研究了基于三种不同拉电子结构单元所形成的聚合物,在光物理性质、电化学性能、聚合物固体薄膜分子堆积以及光电转化效率等方面的性能差异。研究结果表明,三种聚合物热失重5%的温度都在340℃以上,均具备制备光伏器件的热稳定性条件。FTT单元作为拉电子结构单元所得到的聚合物PSB-FTT具有最大的吸收光子能力、最强的分子间π-π堆积、最有效的激子分离和最高的空穴传输性能,从而导致基于聚合物PSB-FTT的器件具有最佳的PCE值。基于聚合物PSB-DFBT/PC71BM、PSB-DTDFBT/PC71BM和PSB-FTT/PC71BM的BHJ PSCs器件效率分别为1.88%(Voc=0.76 V,Jsc=6.39 mA cm-2,FF=39%),0.48%(Voc=0.58 V,Jsc=2.97 mA cm-2,FF=28%)和4.55%(Voc=0.82V,Jsc=9.50 mA cm-2,FF=57%)。4.设计并合成了以2-(4-硫烷基)苯基噻吩(SBT)为2D共轭侧链取代的BDT衍生物为推电子结构单元,并将其分别与两种经典的拉电子结构单元DFBT和FTT进行Stille偶联聚合,分别得到聚合物PSBT-DFBT和PSBT-FTT。同时,为了对比研究4-硫烷基苯(SB)与2-(4-硫烷基)苯基噻吩(SBT)两种2D共轭侧链取代BDT对所形成的聚合物光物理性质、电化学性能以及光伏性能的影响,重新合成了聚合物PSB-FTT。详细地研究了侧链结构对三种聚合物的光物理性质、电化学性能、结晶性、聚集态结构以及光电能量转换的影响关系。研究结果表明,由于侧链SBT适当延长了分子共轭长度,且与BDT单元直接相连的噻吩基团相比苯环基团具有更小的扭转位阻,聚合物PSBT-FTT相比于PSB-FTT具有更宽、更强的吸收光谱,更强的分子间相互作用力,更小的分子间π-π堆积距离,更高的空穴迁移率。基于PSBT-FTT/PC71BM的BHJ PSCs的器件PCE值达到了7.06%(Voc=0.80 V,Jsc=12.60 mA cm-2,FF=70%),相比基于PSB-FTT/PC71BM的BHJ PSCs器件PCE值(4.83%)提高了将近50%。同时,基于PSBT-DFBT/PC71BM的BHJ PSCs器件PCE值为3.96%,这是基于PSB-DFBT/PC71BM的BHJ PSCs器件PCE值(1.88%)的两倍。这些研究结果表明,SBT侧链比SB侧链更适合于聚合物光伏材料。5.设计并合成了一个基于苯并[1,2-b:3,4-b':5,6-b']三噻吩(BTT)为中心核,3个PDI为臂的“三叶型”有机电子受体材料(BTT-3PDI),采用TGA、DSC、UV-Vis、CV、WAXRD、AFM等表征手段对BTT-3PDI的热性能、光物理性质、电化学性能、分子固体薄膜聚集态形貌等进行了全面分析。研究结果表明,BTT-3PDI具有一定的结晶性,其电子迁移率达到了3.69×10-3 cm2 V-1 s-1。BTT-3PDI与经典的给体材料PTB7-Th具有良好的光谱互补和能级匹配。然而,由于BTT-3PDI与PTB7-Th共混薄膜的微相分离尺寸过小(表面粗糙度RMS小于1 nm),单一相纯度较低,导致共混薄膜激子复合严重,电荷传输性能较差,其共混薄膜的电子迁移率和空穴迁移率分别降至1.67×10-5 cm2 V-1 s-1和2.80×10-5cm2 V-1 s-1,这导致其BHJ PSCs器件的光伏性能较差,PCE值仅为1.35%(Voc=0.78V,Jsc=6.16 mA cm-2,FF=28%)。该研究结果表明,当PDI臂与核具有小角度的结晶性小分子受体材料在光活性共混膜中也能避免严重聚集并出现相分离。
[Abstract]:This paper briefly introduces the principle of the photoelectric conversion of the bulk heterojunction (BHJ) type polymer solar cell (PSCs) and the influence factors of its performance. This paper focuses on the summary of the polymer electron donor material in the BHJ PSCs photosensitive layer, which is represented by the [1,2-b:4,5-b 'two thiophene (BDT) as the representative unit and the PDI (PDI) as the representative. Research progress and design strategy for small molecular electron acceptor materials. In the structure of BHJ PSCs devices, the absorption photon ability of materials in the photosensitive active layer, molecular energy level, solubility, aggregation state, photoactive layer morphology and carrier mobility are all important effects on the photoelectric conversion efficiency (PCE) of the devices. Therefore, this paper regulates the photosensitivity The absorption spectra of the materials in the active layer, the HOMO/LUMO energy level, the solubility, the structure of the blend microphase separation and the carrier mobility are designed and synthesized. A series of new polymer donor materials based on the BDT as the electronic structure unit and the small molecule of the PDI as the tensile electron structure unit are designed and synthesized, and the time of flight time mass spectrometry is used. Magnetic resonance hydrogen spectrum (carbon spectroscopy), elemental analysis and high resolution mass spectrometry have been used to characterize the synthesized target molecules and polymers. At the same time, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), ultraviolet visible absorption spectroscopy (UV-Vis), cyclic voltammetry (CV), wide-angle X ray diffraction (WAXRD), atomic force microscopy (AFM) and so on Methods the thermal properties, crystallinity, photophysical properties, electrochemical properties and surface morphology of the conjugated polymer donor materials and small molecule receptor materials were characterized. The photoelectric energy of the BHJ PSCs device with the target conjugated polymer as the electron donor material or the target receptor subdivision as the receptor material was also studied. The main research contents of this paper are as follows: 1. two kinds of regular three elements are designed and synthesized, which are based on D (BDT), D, benzo [c][1,2,5] thiothiazole as weak electronic structure unit (A1), pyrrole and [3,4-c] pyrrole two ketone (DPP) or isoindigo (ID) as a strong tensile electronic structure unit (A2). Yoke polymers (D-A1-D-A2) PTer-DPP and PTer-ID. have been studied in detail. The effects of the type of A2 on the photophysical properties, electrochemical properties and photoelectric energy conversion of a regular three element conjugated polymer have been studied. The results show that the absorption of PTer-ID in the short wave region (300-550 nm) is stronger than that of PTer-DPP, and the polymer PTer-ID has a good effect. The PTer-ID blend film has a higher hole mobility than the PTer-DPP blend film, so the PSC device shows a higher Jsc (10.01 mA cm-2), and the HOMO level of PTer-ID is lower, so the PSC device shows a higher Voc (0.89V); therefore, no additional additives and optimal treatment conditions are added. The BHJ PSCs photovoltaic device based on the polymer PTer-ID is 3.27%. and the PTer-DPP based device PCE value is only 2.28%.2. with thiophene and [3,2-b] thiophene unit instead of thiophene unit. Two thiophene and [3,2-b] thiophene units are designed and synthesized in the main chain and side chain respectively, and the electronic structure unit is in the D-A type of the conjugate side chain. Conjugated polymers PTT-DTBT and PT-DTTBT. and the effects of thiophene and [3,2-b] Thiophene Units on the thermal, photophysical, electrochemical properties and photoelectric conversion properties of the polymer in the polymer main chain or the conjugate side chain are investigated. The results show that the thiophene and [3,2-b] thiophene units are in the main chain. Polymer PTT-DTBT, thiophene and [3,2-b] thiophene unit located in the conjugate side chain have a wider and more red shift absorption spectrum, smaller optical band gap, higher hole mobility and better film blends. Under the conditions of no additive and post treatment, B based on polymer PTT-DTBT/PC61BM and PT-DTTBT/PC61BM The efficiency of HJ PSCs devices is 3.05% (Voc=0.82 V, Jsc=8.10 mA cm-2, FF=46%) and 4.07% (Voc=0.79 V, Jsc=9.99 mA), designed and synthesized. 4,7- (double (5- bromine -4- hexyl) -2- thiophene) 5,6- two fluoro benzothiothiophene (DTDFBT) and 2- ethyl hexyl -4,6- dibromine -3- fluorothiophene and [3,4-b] thiophene -2- formate are coupled and polymerized, and three kinds of conjugated polymers are obtained and studied in detail based on three different electronic structure sheets. The properties of the polymer formed by the element are in the light physical properties, the electrochemical performance, the accumulation of polymer solid film molecules and the photoelectric conversion efficiency. The results show that the temperature of the three kinds of polymers is above 340 degrees centigrade, and the thermal stability of the photovoltaic devices is prepared by the.FTT unit as the tensile electronic structure. The polymer PSB-FTT obtained by the element has the maximum absorption photon ability, the strongest intermolecular pion pion accumulation, the most effective exciton separation and the highest hole transmission performance, resulting in the best PCE value of the devices based on the polymer PSB-FTT. Based on the BHJ PSCs devices of polymer PSB-DFBT/PC71BM, PSB-DTDFBT/PC71BM and PSB-FTT/PC71BM The efficiency is 1.88% (Voc=0.76 V, Jsc=6.39 mA cm-2, FF=39%), and 0.48% (Voc=0.58 V, Jsc=2.97 mA cm-2, FF=28%) and 4.55% are designed and synthesized. Stille coupling polymerization of substructural units DFBT and FTT was used to obtain polymer PSBT-DFBT and PSBT-FTT. respectively. In order to compare the effects of 4- thiophenyl benzene (SB) and 2- (4- sulfur alkyl) phenyl thiophene (SBT) two 2D conjugated side chains instead of BDT pairs on the photophysical properties, electrochemical properties and photovoltaic properties of the polymers, the effects of SB and 2- (4- sulfur alkyl) phenyl thiophene (SBT) were resynthesized. Polymer PSB-FTT. has studied the effects of side chain structure on the photophysical properties, electrochemical properties, crystallinity, aggregation structure and photoelectric energy conversion of three kinds of polymers. The results show that the side chain SBT extends the molecular conjugation length appropriately, and the thiophene group directly connected to the BDT monomer is compared to the benzene ring group. Smaller torsional resistance, polymer PSBT-FTT has a wider spectrum, stronger absorption spectrum, stronger intermolecular interaction, smaller intermolecular pion accumulation distance and higher hole mobility. The PCE value of BHJ PSCs based on PSBT-FTT/PC71BM has reached 7.06% (Voc=0.80 V, Jsc=12.60 mA cm-2, FF=70%), compared to those based on The PCE value (4.83%) of the BHJ PSCs device (4.83%) increased by nearly 50%. while the PSBT-DFBT/PC71BM based BHJ PSCs device PCE value was 3.96%, which was based on PSB-DFBT/PC71BM BHJ PSCs device two times (1.88%). Benzo [1,2-b:3,4-b': 5,6-b'] three thiophene (BTT) is a central nucleus and 3 PDI "three leaf" organic electron acceptor material (BTT-3PDI). Using TGA, DSC, UV-Vis, CV, WAXRD, AFM and so on, the thermal properties, photophysical properties, electrochemical properties, and the aggregation morphology of molecular solid film are comprehensively analyzed. It is clear that BTT-3PDI has a certain crystalline property, and its electron mobility reaches 3.69 * 10-3 cm2 V-1 s-1.BTT-3PDI and has good spectral complementarity and energy level matching with the classical donor PTB7-Th. However, because the microphase separation size of the BTT-3PDI and PTB7-Th blend films is too small (the surface roughness RMS is less than 1 nm), the purity of the single phase is low, and the purity of the single phase is low. The composite film has a serious complex of excitons and poor charge transfer performance. The electron mobility and hole mobility of the blend films are reduced to 1.67 x 10-5 cm2 V-1 S-1 and 2.80 x 10-5cm2 V-1 s-1, which leads to the poor photovoltaic performance of the BHJ PSCs devices, and the PCE value is only 1.35% (Voc=0.78V, Jsc=6.16 mA). Small crystalline acceptor materials with small angles can also avoid serious aggregation and phase separation in photo active blend films.

【学位授予单位】：湘潭大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TB34;TM914.4

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