Cd基化合物纳米晶-有机聚合物杂化太阳能电池研究进展

有机-无机杂化太阳能电池因其结合了有机材料和无机材料各自的优势而引起了人们的广泛关注和研究. Cd基化合物纳米晶因其具有制备方法简单、尺寸及形貌可控、载流子迁移率高和稳定性好等优点而成为最早被研究的一类无机受体. 本文介绍了有机-无机杂化太阳能电池的结构及原理, 分析了影响有机-无机杂化太阳能电池效率的三个主要因素, 分别是开路电压(V_oc)、短路电流(J_sc)和填充因子(FF). 从改善Cd基化合物纳米晶的合成方法, 增加Cd基化合物纳米晶和有机聚合物间的界面接触, 以及优化Cd基化合物纳米晶和有机聚合物所用溶剂和所占比例等方面阐述了近年来Cd基化合物纳米晶-有机聚合物杂化太阳能电池的研究进展. 并展望了Cd基化合物纳米晶-有机聚合物杂化太阳能电池的发展方向.     

富勒烯类界面修饰材料在聚合物太阳能电池中的应用

聚合物太阳能电池具有质量轻、成本低、可大面积柔性制备等优点,近年来成为国内外研究的热点.界面修饰是实现器件效率最大化的有效途径.与无机、高分子类界面修饰材料相比,富勒烯类界面修饰材料因富勒烯本身良好的电子亲和性及与受体分子结构相似而表现出优异的兼容性,在提高聚合物太阳能电池性能方面表现尤为突出.本文介绍了聚合物太阳能电池的结构与光伏参数,综述了富勒烯衍生物作为界面修饰材料,在聚合物太阳能电池中的研究进展,并对富勒烯类界面修饰材料的进一步发展进行了探讨.     

PTh / ZnO复合纳米粉的固相合成及其光谱特性

0引言导电聚合物/无机物纳米复合材料具有纳米材料和导电聚合物的共同特性,因此在电催化、二次充电电池材料、超级电容器材料等方面具有良好的应用前景[1]。聚噻吩(PTh)以及取代聚噻吩是导电聚合物领域中较早发现的具有环境稳定性和可加工性的材料之一。近年来,有关聚噻吩/无机物纳米复合材料的制备及其光电性能的研究倍受关注,Gebeyehu等[2]用PTh敏化纳米晶TiO2光伏电池,发现其光伏效率明显优于固态光伏电池;Jayant等[3]研究了PTh中的羧基基团的影响以及在纳米晶TiO2     

LiFePO4纳米晶的尺寸、形貌调控及锂电池性能研究

由于材料的电化学性能与其尺寸、形貌和结构密切相关,本文围绕乙二醇体系制备LiFePO_4纳米晶展开了材料的尺寸和形貌调控合成探索,并对材料进行了锂电池性能表征。改变体系的反应物浓度,LiFePO_4纳米晶的尺寸明显发生变化,当体系中FeSO_4的浓度为0.15mol/L时,得到的LiFePO_4纳米晶尺寸最小,其锂离子电池的容量稍高于其他尺寸的LiFePO_4纳米晶。葡萄糖的添加量对LiFePO_4纳米晶的形貌会产生影响,但对锂离子电池性能影响不大。     

聚合物太阳能电池阴极修饰层研究进展

聚合物太阳能电池以其质量轻、成本低、制备工艺简单等优点成为清洁能源利用的研究热点.近年来聚合物太阳能电池光电转换效率逐步提高,单结聚合物太阳能电池的光电转换效率已超过11%,其中器件的界面修饰层成为影响器件光伏性能的重要因素.本文总结了聚合物太阳能电池阴极修饰层的研究进展,分别从无机材料和有机材料两方面介绍了常用的阴极修饰层材料.无机材料包括金属氧化物、金属和金属化合物等,有机材料包括聚合物、富勒烯衍生物以及n-型有机半导体材料等.本文还从阴极修饰层的电学特性、光学特性、能级位置、表面形貌、界面接触等方面讨论了其对聚合物太阳能电池光伏性能的影响,展望了聚合物太阳能电池的发展前景.     

电沉积ZnO纳米棒阵列及共形结构杂化太阳能电池

采用电沉积法制备出ZnO致密纳米颗粒膜和不同尺寸的纳米棒阵列。通过在ZnO上旋涂p型聚合物聚3-己基噻酚（P3HT）与n型富勒烯衍生物[6,6]-苯基-C61丁酸甲酯（PCBM）的混合物,并蒸镀金属Ag,制备出不同结构的杂化太阳能电池。通过扫描电镜、X射线衍射、光致发光和模拟太阳光光电性能测试,对ZnO的生长条件、晶体形貌及缺陷与太阳能电池性能之间的关系进行了系统研究。结果表明,ZnO的形貌和晶体缺陷的分布对杂化太阳能电池有重要影响,避免共混聚合物与ZnO缺陷聚集区的直接接触可有效消除电流泄漏。在电池结构方面,与ZnO纳米阵列块状结构杂化太阳能电池相比,共形结构的杂化太阳能电池可有效缩短空穴到金属电极的传输距离,增大聚合物与金属电极的接触面积,光电转换效率可提升64%~101%。     

聚合物太阳能电池给体材料研究进展

随着能源和环境问题日益严重,人们日益关注于太阳能的开发和应用。同时,无机太阳能电池因其自身原因而受到限制,聚合物太阳能电池受到更多的关注。在聚合物基的太阳能电池中,给体材料制约着电池效率的提高,其中材料的带隙和能级是影响其性能的主要因素。而通过研究和选取具有合适带隙和能级的给体材料可以有效地调节电池器件的效率。本文介绍了太阳能电池给体材料的设计原则与主要影响因素,并叙述了近年来该领域内的研究进展和以及发展前景。     

Sr3Al2O6:Eu2+红色发光纳米晶的新型形貌与发光性能的研究

对于稀土发光纳米晶来讲,产品颗粒尺寸与形貌不仅对发光性能有影响,而且直接影响其应用[1,2].如颗粒尺寸在1～10 μm之间且形貌接近于球形的发光微米晶在涂屏时发光效率是最高的,而具有新型微观结构与形貌的稀土发光纳米晶,如纳米线、纳米棒及具有自组装特性的花晶等纳米结构材料由于在纳米发光器件方面有着潜在的应用价值,已成为当今纳米科学的研究焦点.     

电沉积ZnO纳米棒阵列及共形结构杂化太阳能电池

采用电沉积法制备出ZnO致密纳米颗粒膜和不同尺寸的纳米棒阵列。通过在ZnO上旋涂p型聚合物聚3-己基噻酚(P3HT)与n型富勒烯衍生物[6,6]-苯基-C61丁酸甲酯(PCBM)的混合物,并蒸镀金属Ag,制备出不同结构的杂化太阳能电池。通过扫描电镜、X射线衍射、光致发光和模拟太阳光光电性能测试,对ZnO的生长条件、晶体形貌及缺陷与太阳能电池性能之间的关系进行了系统研究。结果表明,ZnO的形貌和晶体缺陷的分布对杂化太阳能电池有重要影响,避免共混聚合物与ZnO缺陷聚集区的直接接触可有效消除电流泄漏。在电池结构方面,与ZnO纳米阵列块状结构杂化太阳能电池相比,共形结构的杂化太阳能电池可有效缩短空穴到金属电极的传输距离,增大聚合物与金属电极的接触面积,光电转换效率可提升64%~101%。     

SnO2表面卤化提高钙钛矿太阳能电池光伏性能

钙钛矿太阳能电池(PSCs)成为近几年来迅速发展的新型太阳能电池,其中将SnO₂纳米粒子层用作电子传输层(ETL)的钙钛矿太阳能电池器件得到了广泛的关注。SnO₂有着更低的制备温度,使其具备应用于柔性器件的潜力,但与钙钛矿层能级不匹配等问题限制着其发展。而在界面处加入钝化层,尤其是表面卤化的方法或可解决这一问题。本文综合研究了SnO₂表面卤化对钙钛矿太阳能电池光伏性能的影响,选用四丁基氯化铵(TBAC)、四丁基溴化铵(TBAB)和四丁基碘化铵(TBAI)三种钝化材料对SnO₂表面进行钝化处理,并对钝化材料溶液进行了浓度梯度研究。通过材料形貌、结构和光学性能表征以及电池器件性能测试分析等方法,证明了SnO₂表面卤化可提高钙钛矿层的质量和PSCs光伏性能,并从器件内部电荷传输动力学等角度解释了器件性能改善的原因。为进一步说明其性能改善的机理,采用基于密度泛函理论(DFT)的第一性原理计算方法对材料表面性质进行了深入研究,从能量、结构、电荷密度、态密度、功函数等角度解释了表面卤化提高SnO₂/钙钛矿界面处电子传输特性的原因。实验和理论计算均表明TBAC对于SnO₂具有较好的钝化效果,并随着溶液浓度的提升钝化作用越明显。SnO₂表面卤化作用的深入研究不仅对提高电池器件性能具有实际意义,还能够帮助理解太阳能电池界面现象,为界面改性提供新的研究思路。     

Constraints in post-synthesis ligand exchange for hybrid organic (MEH-PPV)–inorganic (CdSe) nanocomposites

For an optimum charge/energy transfer performance of hybrid organic–inorganic colloidal nanocrystals for applications such as photonic devices and solar cells, the determining factors are the distance between the nanocrystal and polymer which greatly depends upon nanocrystal size/nanocrystal ligands. Short chain ligands are preferred to ensure a close contact between the donor and acceptor as a result of the tunnelling probability of the charges and the insulating nature of long alkyl chain molecules. Short distances increase the probability for tunnelling to occur as compared to long distances induced by long alkyl chains of bulky ligands which inhibit tunnelling altogether. The ligands on the as-synthesized nanocrystals can be exchanged for various other ligands to achieve desirable charge/energy transfer properties depending on the bond strength of the ligand on the nanocrystal compared to the replacement ligand. In this work, the constraints involved in post-synthesis ligand exchange process have been evaluated, and these factors have been tuned via wet chemistry to tailor the hybrid material properties via appropriate selection of the nanocrystal capping ligands. It has been found that both oleic acid and oleylamine (OLA)-capped cadmium selenide (CdSe) quantum dots (QDs) as compared with trioctylphosphine oxide (TOPO)-passivated CdSe QDs are of high quality, and they provide better steric stability against coagulation, homogeneity, and photostability to their respective polymer:CdSe nanocomposites. CdSe QDs particularly with OLA capping have relatively smaller surface energies, and thus, lesser quenching capabilities show dominance of photoinduced Forster energy transfer between donors (polymer) and acceptors (CdSe nanocrystals) as compared to charge transfer mechanism as observed in polymer:CdSe (TOPO) composites. It is conjectured that size quantization effects, stereochemical compatibility of ligands (TOPO, oleic acid, and oleyl amine), and polymer MEH-PPV stability greatly influence the photophysics and photochemistry of hybrid polymer–semiconductor nanocomposites.     

Interplay of three-dimensional morphologies and photocarrier dynamics of polymer/TiO2 bulk heterojunction solar cells

In this study, we investigated the interplay of three-dimensional morphologies and the photocarrier dynamics of polymer/inorganic nanocrystal hybrid photoactive layers consisting of TiO(2) nanoparticles and nanorods. Electron tomography based on scanning transmission electron microscopy using high-angle annular dark-field imaging was performed to analyze the morphological organization of TiO(2) nanocrystals in poly(3-hexylthiophene) (P3HT) in optimal solar cell devices. The Three-dimensional (3D) morphologies of these hybrid films were correlated with the photocarrier dynamics of charge separation, transport, and recombination, which were comprehensively probed by various transient techniques. Visualization of these 3D bulk heterojunction morphologies clearly reveals that elongated and anisotropic TiO(2) nanorods in P3HT not only can significantly reduce the probability of the interparticle hopping transport of electrons by providing better connectivity with respect to the TiO(2) nanoparticles, but also tend to form a large-scale donor-acceptor phase-separated morphology, which was found to enhance hole transport. The results support the establishment of a favorable morphology for polymer/inorganic hybrid solar cells due to the presence of the dimensionality of TiO(2) nanocrystals as a result of more effective mobile carrier generation and more efficient and balanced transport of carriers.     

杂化太阳电池中异质结界面的修饰及其对电池光电性能的影响

有机-无机杂化太阳电池综合了有机、无机材料的优点,成本低、理论效率高,受到人们的广泛关注.杂化太阳电池的光活性层由无机半导体和有机共轭聚合物复合而成.当光照射到活性层上时,共轭聚合物吸收光子产生激子(电子-空穴对);激子迁移到有机给体-无机受体的异质结界面处发生解离而产生自由电子和空穴;自由电子和空穴分别向无机半导体和有机聚合物传输,从而实现电荷的分离和传导.激子在有机-无机异质结界面处的分离效率是影响电池性能的一个重要因素.有机、无机两相材料往往因为接触面积小以及相容性差使此两相材料接触不佳,激子迁移到此界面不能有效分离,从而严重影响了杂化太阳电池的效率.这个问题可以通过此界面的修饰加以改善.本文即综述了有机-无机异质结界面修饰的方法、作用和意义,并展望了杂化太阳电池未来的发展趋势和应用前景.     

Trigonal pyramidal CuInSe2 nanocryastals derived by a new method for photovoltaic applications

Copper indium selenide (CuInSe₂) nanocrystals with trigonal pyramidal shape are synthesized by a two-step process for photovoltaic applications. Structural, morphological and optical properties of the as-synthesized CuInSe₂ nanocrystals are characterized by using powder X-ray diffraction analysis, transmission electron microscopy, X-ray photoelectron spectroscopy and UV-Vis absorption spectroscopy. Results indicate that the monodispersed nanocrystals show a single phase polycrystalline and the size of the trigonal pyramid is in the range of 10-12 nm, and the average composition ratio of the Cu/In/Se is measured to be 1.0:1.2:2.0. It is also investigated that the size and morphology of the CuInSe₂ nanocrystals can be tuned through a manipulation of the reaction time. Under an illumination of the simulated AM 1.5, the as-fabricated hybrid solar cell based on the P3HT/CuInSe₂ nanocrystals blends exhibits a promising open circuit voltage (V_oc) of 0.42 V and its energy conversion efficiency is as 3 times as that of the solar cell fabricated by only the naked P3HT polymer.     

Hybrid polymer/nanoparticle solar cells: preparation, principles and challenges

Hybrid polymer/nanoparticle solar cells have a light harvesting layer composed of semiconducting inorganic nanoparticles and a semiconducting conjugated polymer. They have potential to give high power conversion efficiencies (PCE). However, the PCE values reported for these solar cells are not currently as high as anticipated. This article reviews the main methods currently used for preparing hybrid polymer/nanoparticle solar cells from the colloid perspective. PCE data for the period of 2005-2011 are presented for hybrid polymer/nanoparticle solar cells and compared to those from polymer/fullerene cells. The key reasons for the relatively low PCE values for hybrid polymer/nanoparticle solar cells are uncontrolled aggregation and residual insulating ligands at the nanoparticle surface. Two hybrid polymer/nanoparticle systems studied at Manchester are considered in which the onset of aggregation and its affect on composite film morphology were studied from the colloidal perspective. It is concluded that step-change approaches are required to increase the PCEs of hybrid polymer/nanoparticle solar cells and move them toward the 10% value required for widespread commercialisation. A range of nanoparticles that have potential for application in possible longer term terawatt solar energy production are discussed.     

Role of surface modification of colloidal CdSe quantum dots on the properties of hybrid organic–inorganic nanocomposites

In this work, tri-octyl phosphine/tri-octyl phosphine oxide (TOPO)-capped cadmium selenide (CdSe) quantum dots (QDs) of varied sizes (5–9 nm), prepared by varying the input Cd:Se precursor ratio using chemical route, were dispersed in conducting polymer matrices viz. poly[2-methoxy, 5-(2-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) and poly(3-hexylthiophene) (P3HT). By using a binary solvent mixture (pyridine–chloroform), homogeneous dispersion of CdSe nanocrystals in polymers (MEH-PPV, P3HT) could be realized. The properties of the resulting dispersions could be tailored by the composition and concentration of QDs in polymer. The emission and structural properties of polymer–CdSe nanocomposites are found to be dependent on the crystallite size and morphology of CdSe nanocrystallites. An effective quenching of photoluminescence emission in the polymer nanocomposite was observed for smaller CdSe quantum dots (size ∼6 nm) as compared to larger CdSe quantum dots (size ∼9 nm), thus ensuring efficient charge transfer process across the polymer–CdSe interface in the former case. The incomplete quenching, particularly for MEH-PPV:CdSe nanocomposites, could be as a result of insufficient coverage of polymers on the surface of CdSe nanocrystallites, mainly due to phase segregation for TOPO-stripped CdSe nanocrystallites. The superior morphology and optical properties of polymer nanocomposite (P3HT:CdSe QDs) could play a pivotal role for the realization of effective charge separation and transport in hybrid solar cells.     

Self-vertical phase separation study of nanoparticle/polymer solar cells by introducing fluorinated small molecules

A new approach to induce self-vertical phase separation of nanoparticle/polymer hybrid solar cells is reported by introducing fluorinated small molecules into the active layer. The formation of a vertically gradient structure improves not only polymer organization but also charge transport efficiency, thus increasing the photovoltaic cell performance by a factor of 5.     

Ultrafast Charge Transfer and Upconversion in Zinc β‐Tetraaminophthalocyanine‐Functionalized PbS Nanostructures Probed by Transient Absorption Spectroscopy

We functionalize PbS nanocrystals with the organic semiconductor Zn β‐tetraaminophthalocyanine to design a nanostructured solid‐state material with frequent organic–inorganic interfaces. By transient absorption and fluorescence spectroscopy, we investigate the optoelectronic response of this hybrid material under near‐infrared excitation to find efficient charge transfer from the nanocrystals to the molecules. We demonstrate that the material undergoes cooperative sensitization of two nanocrystals followed by photon upconversion and singlet emission of the organic semiconductor. The upconversion efficiency resembles that of comparable systems in solution, which we attribute to the large amount of interfaces present in this solid‐state film. We anticipate that this synthetic strategy has great prospects for increasing the open‐circuit voltage in PbS nanocrystal‐based solar cells.     

Synthesis of lead chalcogenide nanocrystals and study of charge transfer in blends of PbSe nanocrystals and poly(3-hexylthiophene)

Nearly monodisperse lead chalcogenide (PbE, E = S, Se, or Te) semiconductor quantum dots of controllable shape have been produced via a novel synthesis which includes the occurrence of in situ formed Pb(0) particles. Tunable size and shape are achieved through appropriate choice of the precursor type and the stabilizer. As precursor, we use, on the one hand, lead oxide or lead acetate, on the other hand, tellurium, selenium, or sulfur powder dissolved in trioctylphosphine (TOP), tributylphosphine (TBP), or 1-octadecene (ODE). Oleic acid (OA) and various amines, as well as TOP and TBP are used for stabilization. With respect to possible application in hybrid solar cells, the surface of as-synthesized spherical PbSe nanocrystals was investigated by nuclear magnetic resonance (NMR), mass spectrometry (MS) and thermogravimetric analysis (TGA). As an important result, it was found that the surface is not mostly covered by oleic acid after synthesis, but by a phosphorus compound. We also applied a ligand exchange procedure with hexylamine and found evidence for the successful attachment of hexylamine to the nanocrystal surface. Additionally, charge separation between these nanoparticles and the conjugated polymer poly(3-hexylthiophene) (P3HT) is studied by electron spin resonance and photoinduced absorption spectroscopy. The spectra obtained suggest that charges can be produced successfully by photoinduced charge transfer.