末端功能基团对聚（3-丁基噻吩）光电性能的影响

研究了4种带有不同末端基团的聚(3-丁基噻吩)(P3BT)的光电性能。结果表明,末端基团对P3BT的结晶有一定的抑制作用,可以改变P3BT的表面能,从而有效调控P3BT∶PCBM共混体系相容性以及薄膜的形貌,并影响以P3BT为给体材料的聚合物光伏器件的性能。其中,带有较短烷基链末端基团的烯丙基封端P3BT具有较高的结晶性,与PCBM具有适中的相容性,使得光伏器件的光敏层能够形成理想的微相分离结构,器件效率可以达到3.1%,较传统的溴封端P3BT器件效率提升35%以上。     

用CdSe/ZnS量子点提高体异质结有机太阳电池的效率

通过掺杂吸收光谱在可见光波段的量子点可提高聚合物对可见光的吸收,因此掺杂CdSe/ZnS核-壳结构量子点(CQDs)能提高聚(3-己基噻吩):[6,6]-苯基-C61-丁酸甲酯(P3HT:PCBM)体异质结太阳电池的能量转换效率.本文研究了CdSe/ZnS量子点在P3HT:PCBM中的不同掺杂比例及其表面配体对太阳电池光伏性能的影响,优化器件ITO(氧化铟锡)/PEDOT:PSS(聚(3,4-乙撑二氧噻吩:聚苯乙烯磺酸)/P3HT:PCBM:(CdSe/ZnS)/Al的能量转换效率达到了3.99%,与相同条件下没有掺杂量子点的参考器件ITO/PEDOT:PSS/P3HT:PCBM/Al相比,其能量转换效率提高了45.1%.     

加入NPB提高P3HT:PCBM聚合物太阳能电池光伏性能

研究了在聚3-己基噻吩(P3HT)和[6,6]-苯基-C61-丁酸甲酯(PCBM)共混薄膜中加入第三组分N,N’-二苯基-N,N’-(1-萘基)-1,1’-联苯-4,4’-二胺(NPB)对器件性能的影响。实验发现:加入NPB可以促进P3HT:PCBM本体异质结的生长,进而提高器件的光伏性能,当NPB浓度为0.4mg/mL时,能量转换效率(PCE)从1.05%提高到1.64%。NPB的加入使P3HT在可见光范围内吸收增强,特别是在560nm和610nm处的吸收强度明显增大;扫描电子显微镜(SEM)研究结果表明,NPB的加入增大了P3HT与PCBM的相分离程度,提高了激子分离的几率;空穴单极性电流-电压曲线证明适量NPB的加入改善了薄膜空穴传输性能。     

喷涂法制备大面积倒置聚合物光伏器件

采用喷涂工艺制备了结构为ITO/ZnO/P3HT∶PCBM/V2O5/Ag(P3HT:聚噻吩;PCBM:6,6-苯基-C61-丁酸甲酯)的大面积倒置光伏器件,有效面积为1.0×1.1 cm2。 光谱测试结果表明,退火处理后,P3HT∶PCBM薄膜吸收显著增强,并且产生一定程度的红移。 采用ZnO和V2O5代替LiF和PEDOT∶PSS(聚(3,4-乙撑二氧噻吩)∶聚苯乙烯磺酸盐)作为器件修饰层,避免了PEDOT∶PSS对ITO的腐蚀和LiF潮解,采用Ag代替Al作为金属背电极避免了Al被氧化。 经过后退火处理器件的效率从1.1%提升至1.65%。 器件的稳定性相对于传统结构有了大幅提升,8周后器件效率只衰减10%。     

改善有机光伏器件性能的新型缓冲层

通过热蒸发在ITO阳极和聚3,4-乙撑二氧噻吩:聚苯乙烯磺酸(PEDOT:PSS)层之间引入一层聚四氟乙烯（PTFE）缓冲层,研究聚四氟乙烯缓冲层对基于聚3-己基噻吩:6,6-苯基-C61丁酸甲酯(P3HT:PCBM)的有机光伏器件光电特性影响。与使用PEDOT:PSS作为缓冲层的器件相比,使用聚四氟乙烯缓冲层的有机光伏器件开路电压、短路电流和光电转换效率均有所提高。器件光电性能提高的原因是由于PTFE缓冲层大量带负电荷的氟离子在ITO/PTFE界面处形成偶极子层, 改善了内建电场,从而使得空穴电荷的收集更加有利。     

基底温度对刮涂制备的P3HT:PCBM薄膜形貌和光伏电池性能的影响

研究了刮涂制备P3HT:PCBM(P3HT:聚3-己基噻吩,PCBM:[6,6]-苯基-C61-丁酸甲酯)活性层的过程中,基底温度对P3HT:PCBM活性层薄膜性质和电池性能的影响.结果表明,提高基底温度在缩短薄膜干燥时间的同时,抑制了PCBM相的大尺度聚集,并改善了P3HT:PCBM薄膜中P3HT在(100)方向上的结晶程度,但降低了π-π共轭方向上的有序度.制备的光伏电池经过进一步退火处理后可形成良好的互穿网络结构,能量转换效率可达3.93％.     

给受体共混质量比对P3HT:PCBM薄膜结构和器件性能的影响

以聚3-己基噻吩(P3HT)为给体、[6,6]-苯基-C61-丁酸甲酯(PCBM)为受体的光伏体系作为研究对象,采用溶剂退火的后处理方法制备薄膜样品,利用紫外-可见(UV-Vis)吸收光谱、原子力显微镜(AFM)、X射线衍射(XRD)等测试手段分别对共混膜样品的形貌和结构进行表征,同时利用熵值统计方法对AFM形貌图像进行分析处理.并在此基础上制备太阳能电池器件,其结构为氧化铟锡导电玻璃/聚3,4-乙撑二氧噻吩:聚苯乙烯磺酸盐/聚3-己基噻吩:[6,6]-苯基-C61-丁酸甲酯/金属铝(ITO/PEDOT:PSS/P3HT:PCBM/Al),研究了给受体共混比例(质量比)对活性层薄膜以及电池性能的影响.结果表明,受体PCBM含量的增加会影响P3HT给体相的有序结晶,当给受体比例为1:1时,活性层薄膜具有较宽的紫外-可见吸收特征,且具有较好的相分离和结晶度,基于该样品制备的电池器件其光电转换效率达到三种比例的最大值(2.77%).表明退火条件下,改变给受体比例可以影响活性层的微纳米结构而最终影响电池的光电转换效率.     

齐聚噻吩及其衍生物有机光伏材料

齐聚噻吩及其衍生物具有良好的环境稳定性和优异的光电性能,是一类具有良好发展前景的有机功能材料。本文综述了近年来齐聚噻吩及其衍生物的发展状况,简述了其主要合成方法;根据结构将其分为两大类:一类是不含极性基团或仅含弱极性基团的齐聚噻吩衍生物,另一类是给体-受体型齐聚噻吩衍生物,并讨论了它们作为有机光伏材料的应用。给体-受体型齐聚噻吩衍生物由于分子内的电荷传输作用,其光物理和电化学性能均优于不含极性基团的齐聚噻吩,该类材料在小分子光伏器件中具有最高的光电转换效率(>10%)。文章最后简要分析了影响光伏器件性能的主要因素。     

锌卟啉自组装在染料敏化太阳能电池中的应用

制备了2种锌卟啉天线分子P2与P3，并通过自组装的方法成功地将这些天线分子应用到了染料敏化太阳能电池之中。与传统的D-π-A结构的染料相比，这种策略显示出了明显的优势：可以避免复杂的合成步骤，还可以通过调节天线分子和锚固基团的结构去改善染料的光子捕获能力并减少电荷复合行为。当4-吡啶-4-基苯甲酸（A）作为锚固基团时，经过分子自组装之后，基于A-P2的电池器件显示出了1.68%的转换效率，开路电压为526 mV，短路电流密度为5.39 mA·cm^-2，这充分说明了自组装策略在染料敏化太阳能电池中得到了很好的应用。而基于A-P3的电池器件能量转换效率只有0.79%，这可能主要是因为天线分子P3较大的位阻减小了染料吸附量的原因造成的。我们另外也测试比较了它们在光学、电化学、光伏性能等方面的差异。     

给受体共混质量比对P3HT∶PCBM薄膜结构和器件性能的影响

以聚3-己基噻吩(P3HT)为给体、[6,6]-苯基-C61-丁酸甲酯(PCBM)为受体的光伏体系作为研究对象,采用溶剂退火的后处理方法制备薄膜样品,利用紫外-可见(UV-Vis)吸收光谱、原子力显微镜(AFM)、X射线衍射(XRD)等测试手段分别对共混膜样品的形貌和结构进行表征,同时利用熵值统计方法对AFM形貌图像进行分析处理.并在此基础上制备太阳能电池器件,其结构为氧化铟锡导电玻璃/聚3,4-乙撑二氧噻吩∶聚苯乙烯磺酸盐/聚3-己基噻吩:[6,6]-苯基-C61-丁酸甲酯/金属铝(ITO/PEDOT∶PSS/P3HT∶PCBM/Al),研究了给受体共混比例(质量比)对活性层薄膜以及电池性能的影响.结果表明,受体PCBM含量的增加会影响P3HT给体相的有序结晶,当给受体比例为1∶1时,活性层薄膜具有较宽的紫外-可见吸收特征,且具有较好的相分离和结晶度,基于该样品制备的电池器件其光电转换效率达到三种比例的最大值(2.77％).表明退火条件下,改变给受体比例可以影响活性层的微纳米结构而最终影响电池的光电转换效率.     

Quantitative nanoorganized structural evolution for a high efficiency bulk heterojunction polymer solar cell

We have developed an improved small-angle X-ray scattering (SAXS) model and analysis methodology to quantitatively evaluate the nanostructures of a blend system. This method has been applied to resolve the various structures of self-organized poly(3-hexylthiophene)/C61-butyric acid methyl ester (P3HT/PCBM) thin active layer in a solar cell from the studies of both grazing-incidence small-angle X-ray scattering (GISAXS) and grazing-incidence X-ray diffraction (GIXRD). Tuning the various length scales of PCBM-related structures by a different annealing process can provide a flexible approach and better understanding to enhance the power conversion of the P3HT/PCBM solar cell. The quantitative structural characterization by this method includes (1) the mean size, volume fraction, and size distribution of aggregated PCBM clusters, (2) the specific interface area between PCBM and P3HT, (3) the local cluster agglomeration, and (4) the correlation length of the PCBM molecular network within the P3HT phase. The above terms are correlated well with the device performance. The various structural evolutions and transformations (growth and dissolution) between PCBM and P3HT with the variation of annealing history are demonstrated here. This work established a useful SAXS approach to present insight into the modeling of the morphology of P3HT/PCBM film. In situ GISAXS measurements were also conducted to provide informative details of thermal behavior and temporal evolution of PCBM-related structures during phase separation. The results of this investigation significantly extend the current knowledge of the relationship of bulk heterojunction morphology to device performance.     

Ternary Donor–Insulator–Acceptor Systems for Polymer Solar Cells

A series of block copolymers with fixed length of the semiconductor‐block poly(3‐butylthiophene) (P3BT) and varying length of the insulator‐block polystyrene (PS) are synthesized. These copolymers are blended with phenyl‐C61‐butyric acid methyl ester (PCBM) for the bulk heterojunction photoactive layers. With appropriate insulator‐block length and donor–acceptor ratio, the power conversion efficiency increases by one order of magnitude compared with reference devices with pure P3BT/PCBM. PS blocks improve the miscibility of the active layer blends remarkably. The P3BT‐b‐PS crystallizes as nanorods with the P3BT core covered with the PS‐block, which creates a nanoscale tunneling barrier between donor and acceptor leading to more efficient transportation of charge carriers in the semiconductors.     

Vertical phase separation of conjugated polymer and fullerene bulk heterojunction films induced by high pressure carbon dioxide treatment at ambient temperature

The morphology of bulk-heterojunctions (BHJ) is critically important for conjugated polymer and fullerene blend solar cells. To alter the morphology, high pressure (gas phase) carbon dioxide (CO(2)) treatment is applied to poly(3-hexyl thiophene) (P3HT) and [6,6]-phenyl-C61 butyric acid methyl ester (PCBM) blend films under ambient temperature. This process can achieve vertically phase separated morphology such that PCBM distributes toward the film surface, which is suggested by secondary ion mass spectroscopy (SIMS), contact angle, X-ray photoelectron spectroscopy (XPS) and cross-sectional scanning electron microscope (SEM) studies. While pristine P3HT films do not show a significant change upon CO(2) treatment, pristine PCBM films are plasticized in high pressure CO(2). Thus, PCBM is selectively plasticized by CO(2) in the blend film and is drawn towards the surface due to depressed surface energy, although P3HT tends to distribute around the surface without CO(2). This stratification process can enhance solar cell performance. 55% improvement is achieved in the power conversion efficiency of the CO(2) treated device compared to the untreated one, indicating that CO(2) treatment can be a good candidate for optimizing the morphology and enhancing the performance of BHJ polymer solar cells.     

Controlling film morphology in conjugated polymer:fullerene blends with surface patterning

We study the effects of patterned surface chemistry on the microscale and nanoscale morphology of solution-processed donor/acceptor polymer-blend films. Focusing on combinations of interest in polymer solar cells, we demonstrate that patterned surface chemistry can be used to tailor the film morphology of blends of semiconducting polymers such as poly-[2-(3,7-dimethyloctyloxy)-5-methoxy-p-phenylenevinylene] (MDMO-PPV), poly-3-hexylthiophene (P3HT), poly[(9,9-dioctylflorenyl-2,7-diyl)-co-benzothiadiazole)] (F8BT), and poly(9,9-dioctylfluorene-co-bis-N,N'-(4-butylphenyl)-bis-N,N'-phenyl-1,4-phenylendiamine) (PFB) with the fullerene derivative, [6,6]-phenyl-C(61)-butyric acid methyl ester (PCBM). We present a method for generating patterned, fullerene-terminated monolayers on gold surfaces and use microcontact printing and Dip-Pen Nanolithography (DPN) to pattern alkanethiols with both micro- and nanoscale features. After patterning with fullerenes and other functional groups, we backfill the rest of the surface with a variety of thiols to prepare substrates with periodic variations in surface chemistry. Spin coating polymer:PCBM films onto these substrates, followed by thermal annealing under nitrogen, leads to the formation of structured polymer films. We characterize these films with Atomic Force Microscopy (AFM), Raman spectroscopy, and fluorescence microscopy. The surface patterns are effective in guiding phase separation in all of the polymer:PCBM systems investigated and lead to a rich variety of film morphologies that are inaccessible with unpatterned substrates. We demonstrate our ability to guide pattern formation in films thick enough to be of interest for actual device applications (up to 200 nm in thickness) using feature sizes as small as 100 nm. Finally, we show that the surface chemistry can lead to variations in film morphology on length scales significantly smaller than those used in generating the original surface patterns. The variety of behaviors observed and the wide range of control over polymer morphology achieved at a variety of different length scales have important implications for the development of bulk heterojunction solar cells.     

Synthesis of all‐conjugated poly(3‐hexylthiophene)‐block‐ poly(3‐(4′‐(3″,7″‐dimethyloctyloxy)‐3′‐pyridinyl)thiophene) and its blend for photovoltaic applications

New all‐conjugated block copolythiophene, poly(3‐hexylthiophene)‐block‐poly(3‐(4′‐(3″,7″‐dimethyloctyloxy)‐3′‐pyridinyl)thiophene) (P3HT‐b‐P3PyT) was successfully prepared by Grignard metathesis polymerization. The supramolecular interaction between [6,6]‐phenyl‐C₆₁‐butyric acid methyl ester (PCBM) and P3PyT was proposed to control the aggregated size of PCBM and long‐term thermal stability of the photovoltaic cell, as evidenced by differential scanning calorimetry (DSC), transmission electron microscopy (TEM), and optical microscopy. The effect of different solvents on the electronic and optoelectronic properties was studied, including chloroform (CL), dichlorobenzene (DCB), and mixed solvent of CL/DCB. The optimized bulk heterojunction solar cell devices using the P3HT‐b‐P3PyT/PCBM blend showed a power conversion efficiency of 2.12%, comparable to that of P3HT/PCBM device despite the fact that former had a lower crystallinity or absorption coefficient. Furthermore, P3HT‐b‐P3PyT could be also used as a surfactant to enhance the long‐term thermal stability of P3HT/PCBM‐based solar cells by limiting the aggregated size of PCBM. This study represents a new supramolecular approach to design all‐conjugated block copolymers for high‐performance photovoltaic devices. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011.     

Photovoltaic Performance and Charge Recombination Dynamics of P3HT/PCBM Blend Heterojunction

We prepared the polymer solar cell based on poly（3-hexylthiophene）（P3HT）/fullerene derivative PCBM（PCBM=[6,6]-phenyl-C61-butyric acid methyl ester） heterojunction and investigated the irradiation intensi- ty-dependent charge recombination dynamics of heterojunction employing nanosecond transient absorption spectroscopy with bias light so as to simulate the photophysical process in heterojunction when the photovoltaic device is on operation. The experimental data exhibit that the yield of free charges gradually decreases and the loss of mobile carriers originated from bimolecular recombination simultaneously increases as the irradiation intensity gradually enhances. This indicates that the polymer solar cell is much suitably used at a low irradiation intensity.