【作者】 刘波；

【导师】 贺跃辉； 邹应萍；

【作者基本信息】 中南大学 ， 材料学， 2013， 博士

【摘要】 聚合物光伏材料的吸收光谱、与富勒烯受体匹配的电化学能级、载流子迁移率和活性层形貌是影响聚合物太阳能能量转换效率的重要因素。本文以拓宽聚合物的吸收光谱、调节电化学能级、提高载流子迁移率和改善活性层形貌为目的,设计与合成了一系列新型的以苯并二呋喃衍生物为核心的共轭聚合物,主要开展的工作如下：(1)一种新的窄带隙共轭聚合物PBDFTT-C,由噻吩并噻吩电子受体单元与苯并二呋喃给体单元通过stille偶联反应合成。通过核磁共振及元素分析验证了聚合物PBDFTT-C的分子结构。研究结果显示,PBDFTT-C拥有一个低的HOMO能级(-5.27eV),在薄膜状态下的吸收波长范围为300～840nm,因此它获得了一个非常窄的光学带隙(1.48eV)。通过空间电荷限制电流法(SCLC)测得它的空穴迁移率为5.4×10-3cm2·V-1·s-1。初始的光伏器件结构为ITO/PEDOT:PSS/PBDFTT-C:PC71BM(1:1.5,w/w)/Ca/Al,当在活性层中加入3%的DIO时,它的能量转换效率提高到4.4%,其中开路电压0.66V,短路电流10.45mA·cm-2,填充因子为0.64。(2)通过Stille偶联反应合成了苯并二呋喃为给体的三种窄带隙聚合物(PBDFDODTBT、PBDFDTBTz和PBDFDTBO)。三种聚合物都能很好的溶解在氯仿、四氢呋喃及氯苯等普通的溶剂中,且它们都具有良好的成膜性。它们的分子结构由核磁共振及元素分析法验证,分子量采用凝胶色谱法(GPC)测定,热学性能由热重分析法(TGA)测定。PBDFDODTBT与PC7,BM按照1：2共混,通过SCLC方法测得它的空穴迁移率达到6.7×10-2cm2·V-1·s-1。当光伏器件结构为ITO/PEDOT: PSS/PBDFDODTBT:PC71BM(1:2, w/w)/Ca/Al,能量转换效率为4.5%,其中开路电压为0.69V,短路电流为9.87mA·cm-2。(3)通过Stille偶联反应合成得到了两种侧链为烷基噻吩的苯并二呋喃类聚合物。所有聚合物都能很好的溶解在普通的溶剂中,且具有良好的成膜性。通过改变不同的电子受体单元来调节聚合物的吸收光谱及电化学能级。聚合物与PC71BM共混通过SCLC方法算得它的的空穴迁移率可达到10-1数量级之高。光伏器件结构为ITO/PEDOT:PSS/PBDFTDTBT:PC71BM(1:1.5, w/w)/Ca/Al时,能量转换效率高达6.0%,相应的开路电压为0.76V,短路电流为12.04mA·cm-2。(4)合成了三种侧链为烷基噻吩的苯并二噻吩类聚合物(PBDTTDTBT、PBDTTDTBP和PBDTTDTBTz)。三种共聚物具有很好的溶解性能、宽阔的紫外可见吸收光谱以及合适的电化学能级。通过改变不同的电子受体来调节聚合物的吸收光谱及电化学能级。通过场效应晶体管法(FET)测得共聚物的空穴迁移率达到10-2数量级,当聚合物与PC71BM共混时,通过SCLC方法测得空穴迁移率高达10-1数量级。光伏器件结构为ITO/PEDOT:PSS/PBDTTDTBO:PC71BM (1:1.5,w/w)/Ca/Al时,能量转换效率为5.9%,开路电压为0.84V,短路电流为11.45mA·cm-2。据我们所知,这是目前报道的以DTBO为受体的共聚物中能量转换效率最高的数值。(5)首次合成了一种侧链含有烷基链的奈并二呋喃为给体单元的聚合物PNDFDTBT。通过核磁共振、凝胶渗透色谱法、热失重分析、紫外吸收光谱、循环伏安法对聚合物PNDFDTBT进行了详细的表征。聚合物PNDFDDTBT与PC71BM按照1：2共混时,通过SCLC方法测得它的空穴迁移率达到7.4×10-2cm2·V-1·s-1.当光伏器件结构为ITO/PEDOT:PSS/PNDFTDTBT:PC71BM(1:2,w/w)/Ca/Al时,在AM1.5,100mW/cm2光照条件下,它的能量转换效率为4.5%。研究结果表明,NDF作为一种新的有前景的电子给体单元将有可能开发出一类高效率的聚合物太阳能电池材料。更多还原

【Abstract】 The absorption spectra and hole mobility of conjugated polymer donor materials are the major factors to affect the power conversion efficiency (PCE) of polymer solar cells (PSCs). This dissertation is focusing on the design and synthesis of new conjugated polymers with broader absorption band and higher hole mobility for improving the photovoltaic properties of the conjugated polymers. The main results are as follows:(1) A new low band-gap conjugated polymers—PBDFTT-C was synthesized from thieno-[3,4-b]thiophene and benzo[1,2-b:4,5-b’] difuran unit by Stille coupling reactions. The structure was verified by’H NMR and elemental analysis, the molecular weight was determined by gel permeation chromatography (GPC) and the thermal property was investigated by thermogravimetric analysis (TGA). PBDFTT-C shows low HOMO energy level of-5.27eV. The polymer film displayed broad absorption in the wavelength region from300nm to840nm with a low bandgap of1.48eV for PBDFTT-C. The field effect hole mobility of PBDFTT-C reached5.4×10-3cm2·V-1·s-1. By using1,8-diiodooctane (DIO) as the solvent additive, photovoltaic cells with the structure of ITO/PEDOT:PSS/PBDFTT-C:PC71BM (1:1.5, w/w)/Ca/Al demonstrated a power conversion efficiency of4.4%with a short circuit current of10.45mA·cm-2, open circuit voltage of0.66V and a fill factor of0.64, under the illumination of AM1.5G,100mW/cm2.(2) Three new low bandgap benzo[1,2-b:4,5-b’]difuran-based conjugated polymers, were synthesized by Stille coupling polymerization reactions. All of the polymers were found to be soluble in common organic solvents such as chloroform, tetrahydrofuran and chlorobenzene with excellent film forming properties. Their structures were verified by1H NMR and elemental analysis, the molecular weights were determined by gel permeation chromatography (GPC) and the thermal properties were investigated by thermogravimetric analysis (TGA). The polymer films exhibit broad absorption bands. The hole mobility of PBDFDODTBT:PC71BM (1:2, w/w) blend reached up to6.7×10-2cm2·V-1·s-1by the space-charge-limited current (SCLC) method. Preliminary photovoltaic cells based on the device structure of ITO/PEDOT:PSS/PBDFDODTBT:PC71BM(1:2,w/w)/Ca/Al showed an open-circuit voltage of0.69V, a power conversion efficiency of4.5%and a short circuit current of9.87mA·cm-2.(3) Two new alkylthienyl substituted benzodifuran(BDF)-based polymers, were synthesized by Stille coupling polymerization reactions. The two polymers were found to be soluble in common organic solvents with excellent film forming properties. The polymers exhibited tunable absorptions and energy levels on incorporation of different electron accepting units. The copolymers blends with PC7)BM exhibited mobility as high as10-1order by the space-charge-limited current (SCLC) method. Preliminary photovoltaic cells based on the device structure of ITO/PEDOT:PSS/PBDFTDTBT:PC71BM(l:1.5, w/w)/Ca/Al showed a power conversion efficiency of6.0%with a high open-circuit voltage (Voc) of0.76V and a short circuit current density(Jsc) of12.04mA·cm-2.(4) Three new alkylthienyl substituted benzodithiophene (BDT)-based polymers, were synthesized by Stille coupling polymerization reactions. All of the polymers were found to be soluble in common organic solvents such as chloroform, tetrahydrofuran and chlorobenzenewith excellent film forming properties. Their structures were verified by elemental analysis and NMR spectroscopy, the molecular weights were determined by gel permeation chromatography (GPC) and the thermal properties were investigated by thermogravimetric analysis (TGA). The polymers exhibited tunable absorptions and energy levels on incorporation of different electron accepting units. All the copolymers showed high field hole mobility up to10-2order, and their blends with PCBM exhibited mobility as high as10-1order by the space-charge-limited current (SCLC) method. Preliminary photovoltaic cells based on the device structure of ITO/PEDOT:PSS/PBDTTDTBO:PC71BM(1:1.5, w/w)/Ca/Al showed a power conversion efficiency of5.9%with a high open-circuit voltage (Voc) of0.84V and a short circuit current density(Jsc) of11.45mA·cm-2. To the best of our knowledge, this is the highest efficiency for dithienyl benzooxadiazole (DTBO)-based polymer solar cells.(5) A new building block of naphtho[1,2-b:5,6-b’]difuran(NDF)with alkyl chains was firstly designed and synthesized. NDF was used as the electron donor unit in constructing a new low band gap copolymer(PNDFDTBT)by a Stille cross-coupling reaction. PNDFDTBT was characterized by NMR spectroscopy, gel permeation chromatography, thermaogravimetric analysis, UV-vis absorption spectroscopy and cyclic voltammetry. Hole mobility and film morphology were investigated in detail. The hole mobility of PNDFDTBT:PC7,BM(1:2, w/w)blend is up to7.4×10"2cm2·V-1·s-1by the space-charge-limited current (SCLC) method. A polymer solar cell with the configuration of ITO/PEDOT: PSS/PNDFDTBT:PC7,BM(1:2, w/w)/Ca/Al demonstrates a promising power conversion efficiency (PCE) of4.5%under the illumination of AM1.5,100mW/cm2. The preliminary and encouraging results in this work show that NDF probably is a new and promising electron donor unit to develop high performance optoelectronic polymers.更多还原