基于小分子噻吩单元的有机太阳能电池研究进展

噻吩及衍生物基团具有独特的光电性能,已广泛应用于有机太阳能电池的设计与合成中,并在有机光电领域发挥着重要的作用。本文综述了近几年来含有噻吩及其衍生物的有机小分子太阳能电池的研究进展。分别综述了含联噻吩、苯并二噻吩和二噻吩并噻咯单元的“给体 受体 给体”型有机供体小分子,并总结了其结构差异。从分子设计的角度出发,探讨分子骨架的共轭程度、链端基团、中心构筑单元数目等改变对材料的光学吸收、能级水平、迁移率等性能的影响,总结了设计高性能的小分子供体材料有效的途径。     

小分子给体/高分子受体型有机太阳能电池研究进展

有机太阳能电池具有低成本、柔性和质量轻等优势, 是一种有应用前景的光伏技术, 受到人们的广泛关注. 有机太阳能电池的光敏活性层通常由p-型有机半导体(包括小分子和高分子)与n-型有机半导体(包括小分子和高分子)共混而成. 小分子给体/高分子受体型有机太阳能电池具有形貌热稳定性优异的特点, 值得深入研究. 本综述旨在总结小分子给体/高分子受体型有机太阳能电池的研究进展, 分别介绍了基于酰亚胺基、氰基和含硼氮配位键(B←N)的高分子受体的活性层材料体系的发展状况. 在器件性能方面, 通过分子设计、相分离形貌调控, 改善了小分子给体/高分子受体的匹配性, 将该类电池的能量转换效率从最初的0.29%提升至目前的9.51%, 为性能的进一步提升总结了经验; 在稳定性方面, 基于该体系形貌热稳定性优异的特点, 开发出高温耐受型有机太阳能电池器件. 最后, 展望了小分子给体/高分子受体型有机太阳能电池的未来发展方向和前景.     

高结晶性小分子给体材料应用于全小分子有机太阳能电池中的研究进展

随着新型小分子给体材料和非富勒烯小分子受体材料的开发和应用, 非富勒烯全小分子有机太阳能电池(NF-ASM OSCs)的光电转换效率已经突破15%, 并逐渐接近聚合物太阳能电池的效率. 相比于聚合物电子给体材料, 小分子电子给体材料拥有其独特的优势, 例如合成批次性差异小、分子量明确和易于提纯等; 但是, 对小分子给体材料的结晶性难于精确调控, 使获得合适的纳米级结构的混合膜仍然是一个挑战. 本综述以给体小分子中心共轭单元的扩展为主线, 从分子设计的角度汇总了近年来对苯并二噻吩、萘并二噻吩和二噻并苯并二噻吩类小分子给体材料的结晶性研究, 并为进一步改善电池活性层形貌和获得更高的光伏性能提供了未来发展的建议.     

非富勒烯聚合物太阳电池研究进展

综述了以p-型共轭聚合物为给体、n-型有机半导体为受体的非富勒烯聚合物太阳电池光伏材料最新研究进展,包括n-型共轭聚合物和可溶液加工小分子n-型有机半导体(n-OS)受体光伏材料,以及与之匹配的p-型共轭聚合物给体光伏材料.介绍的n-型共轭聚合物受体光伏材料包括基于苝酰亚胺(BDI)、萘酰亚胺(NDI)以及新型硼氮键连受体单元的D-A共聚物受体光伏材料,目前基于聚合物给体(J51)和聚合物受体(N2200)的全聚合物太阳电池的能量转换效率最高达到8.26%.n-OS小分子受体光伏材料包括基于BDI和NDI单元的有机分子、基于稠环中心给体单元的A-D-A型窄带隙有机小分子受体材料等.给体光伏材料包括基于齐聚噻吩和苯并二噻吩(BDT)给体单元的D-A共聚物,重点介绍与窄带隙A-D-A结构小分子受体吸收互补的、基于噻吩取代BDT单元的中间带隙二维共轭聚合物给体光伏材料.使用中间带隙的p-型共轭聚合物为给体、窄带隙A-D-A结构有机小分子为受体的非富勒烯聚合物太阳电池能量转换效率已经突破12%,展示了光明的前景.最后对非富勒烯聚合物太阳电池将来的发展进行了展望.     

小分子给体桥联单元烷基链取代位置对光伏器件性能的影响（英文）

设计合成了2个同分异构体小分子给体C2-C-F和C2-M-F,二者仅中间桥联三噻吩单元上烷基链的取代位置不同.研究结果表明,烷基链取代位置对其吸光性能和能级影响较小,但对与受体BTP-4F-12共混后的活性层形貌具有较大影响.其中,小分子给体C2-C-F与受体BTP-4F-12共混的薄膜获得了较好的形貌,光伏器件效率达到12.84%.研究结果表明,可以通过烷基取代的位置来精细调控活性层的形貌,为高效小分子给体的设计提供了有益的参考.     

可溶液加工给体-受体有机小分子太阳能电池材料研究进展

近年来,有机小分子体异质结太阳能电池因其制备工艺简单、廉价、轻便及柔性等优点而备受关注.理想的有机小分子给体材料是提高有机太阳能电池光电转换效率的基础.系统地综述了可溶液加工有机小分子太阳能电池给体材料的研究进展,并对其发展趋势和应用前景做了展望.     

A-D-A型小分子电子给体光伏材料的端基修饰及其光伏性能

有机太阳能电池(OSCs)活性层中的给体材料主要包括共轭聚合物与有机小分子,由于有机小分子给体具有结构确定、易于提纯、重复性高等独特的优势,近年来受到研究工作者的广泛关注。本工作中,我们采取具有良好共平面性的三联苯并二噻吩(TriBDT-T)为推电子(D)中心共轭单元,分别以罗丹宁(RN)、氰基罗丹宁(RCN)和1,3-茚二酮(IDO)为拉电子(A)共轭端基,设计并合成了三种具有A-D-A型结构的小分子给体材料TriBDT-T-RN、TriBDT-T-RCN和TriBDT-T-IDO。我们对比研究了三种端基对其热分解温度、吸收光谱和分子能级等基本性能的影响,并分别将三种小分子给体与非富勒烯型受体材料IT-4F共混制备器件,详细研究了活性层形貌与光伏性能之间的关系。结果表明,不同的A型端基对小分子给体材料的光学性能、电化学性能、光伏器件中活性层的微观形貌以及能量转换效率(PCE)产生显著影响。基于TriBDTT-RN:IT-4F、TriBDT-T-RCN:IT-4F和TriBDT-T-IDO:IT-4F的光伏器件的能量转换效率分别为9.25%、6.31%和6.18%。     

基于1,8-萘酰二胺的具有近红外吸收的π-共轭有机太阳能电池给体材料的分子设计

为了提高有机太阳能电池(Organic solar cells, OSCs)给体材料的光吸收效率,本文设计了系列以噻吩异靛蓝分子片段为中心,不同芳香杂环为π-桥,1,8-萘酰二胺(1,8-Naphthalimide, NI)分子片段为端基的新型π-共轭化合物作为有机太阳能电池给体材料.利用量子化学中的密度泛函理论和含时密度泛函理论方法,对所设计的化合物的光学和电子性质进行了研究,探究分子结构与光谱和电子性质之间的联系.计算结果表明,通过在母体化合物中引入不同的π-桥,可以有效调节所设计分子的前线分子轨道能级、能隙和光谱性质.但是,其对设计分子的几何结构影响不大.设计的化合物分子均具有窄的能隙,在可见光和近红外光谱(NIR)区都有强吸收,这有利于提高有机太阳能电池光吸收效率.前线分子轨道能级分析发现,部分设计的化合物能级与典型富勒烯受体材料相匹配,可选用传统PCBM,bisPCBM和PC₇₁BM作为受体材料,另一部分设计化合物,则应考虑选用其他的太阳能电池受体材料.研究结果表明,本文所设计的化合物可作为具有红光或NIR区有强吸收的高效太阳能电池给体材料应用于太阳能电...     

带有噻吩侧基的有机硼小分子电子受体光伏材料

有机小分子电子受体材料的侧基能够影响异质结有机太阳能电池的给体/受体匹配和器件性能。我们设计并合成了一个硼原子带有噻吩侧基的有机硼小分子(MBN-Th)。该分子的LUMO离域在整个骨架上,HOMO定域在中心核上,其独特的电子结构使该分子具有两个强的吸收峰(波长分别为490和726nm),因此分子具有宽的吸收光谱和强的太阳光吸收能力。与苯基侧基相比,噻吩侧基使分子的HOMO能级下移0.1 eV,LUMO能级保持不变,进而引起分子带隙减小和吸收光谱蓝移20nm。基于该有机硼小分子受体材料的异质结有机太阳能电池,实现了4.21%的能量转化效率和300–850nm的宽响应光谱。实验结果表明,硼原子上的噻吩侧基是调控有机硼小分子光电性质的有效方法,可以用于有机硼小分子受体材料的设计。     

基于受体1-受体2型聚合物给体的高效有机太阳能电池

设计合成了2种宽带隙聚合物给体,分别命名为PDTz-BDD和PDTz-BDT.其中, PDTz-BDT是一种典型的给-受体(D-A)型共轭聚合物, PDTz-BDD是具有受体₁-受体₂(A₁-A₂)型结构的共轭聚合物.采用BTP-e C9作为受体,分别与PDTz-BDD和PDTz-BDT共混构建有机太阳能电池,系统研究了两种给体的光伏性能.研究结果表明,具有A₁-A₂型结构的PDTz-BDD表现出更强的光吸收能力、更明显的溶液聚集效应与更优良的器件形貌,相应的光伏电池可以实现更高的光电转换效率(10.36%).本文不仅设计合成了2种新型给体,而且为构建A₁-A₂型共聚物以开发高效聚合物给体提供了参考.     

叠氮烷烃环加成反应合成C60衍生物及其聚合物太阳电池的特性

通过烷基叠氮化合物与C₆₀的环加成反应合成了一系列以长链烷烃取代C₆₀的亚氨基衍生物,研究了其紫外-可见光吸收特性及电化学性质,并考察了由这些材料和聚[2-甲氧基-5-(2-乙基己氧基)-1,4-对苯乙炔](MEH-PPV)制成的聚合物光电池的性能.这类器件的能量转换效率介于0.13～0.37之间,随着所接烷基链的增长和支链数目的增加,衍生物的溶解度逐步提高,器件的短路电流随着衍生物溶解度的提高而增加,最高可达到1.77mA/cm²,这类器件具有较极大的光暗比,有可能首先在传感器方面得到应用.     

Side chain engineering and conjugation enhancement of benzodithiophene and phenanthrenequnioxaline based conjugated polymers for photovoltaic devices

A series of donor‐acceptor conjugated polymers incorporating benzodithiophene (BDT) as donor unit and phenanthrenequnioxaline as acceptor unit with different side chains have been designed and synthesized. For polymer P1 featuring the BDT unit and alkoxy chains substituted phenanthrenequnioxaline unit in the backbone, serious steric hindrance resulted in quite low molecular weight. The implementation of thiophene ring spacer in polymer P2 greatly suppressed the interannular twisting to extend the effective conjugation length and consequently gave rise to improved absorption property and device performance. In addition, utilizing the alkylthienyl side chains to replace the alkyl side chains at BDT unit in polymer P3 further enhanced the photovoltaic performance due to the increased conjugation length. For polymer P4, translating the alkoxy side chains at the phenanthrenequnioxaline ring into the alkyl side chains at thiophene linker group enhanced molecular planarity and strengthened π?π stacking. Consequently improved absorption property and increased hole mobility were achieved for polymer P4. Our results indicated that side chain engineering not only can influence the solubility of polymer but also can determine the polymer backbone planarity and hence the photovoltaic properties. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1915–1926     

Effect of additive length and chemistry on the morphology of blends of conjugated thiophenes and fullerene derivative acceptor molecules

Small molecule additives have been shown to increase the device efficiency of conjugated polymer (donor) and fullerene derivative (acceptor) based organic solar cells by modifying the morphology of the device active layer. In this paper we conduct a systematic study of how additives affect the donor‐acceptor morphology using molecular dynamics simulations of blends of thiophene‐based oligomers, mimicking poly(3‐dodecylthiophene) (P3DDT) or poly(2,2′:5′,2”‐3,3”‐didocyl‐terthiophene) (PTTT), and fullerene derivatives with additives of varying length and chemical functionalization, mimicking experimentally used additives like methyl ester additives, diiodooctane, and alkanedithiols. We find that functionalization of additives with end groups that are attracted to acceptor molecules are necessary to induce increased donor‐acceptor macrophase separation. In blends where acceptors intercalate between oligomer alkyl side chains, functionalized additives decrease acceptor intercalation. Functionalized additives with shorter alkyl segments increase acceptor macrophase separation more than additives with same chemical functionalization but longer alkyl segments. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 1046–1057     

A Solution‐Processable Molecule using Thieno[3,2‐b]thiophene as Building Block for Efficient Organic Solar Cells

A solution‐processed acceptor‐π‐donor‐π‐acceptor (A‐π‐D‐π‐A) type small molecule, namely DCATT, has been designed and synthesized for the application as donor material in organic solar cells. The fused aromatic unit thieno[3,2‐b]thiophene (TT) flanked with thiophene is applied as π bridge, while 4,8‐bisthienyl substituted benzodithiophene (BDT) and 2‐ethylhexyl cyanoacetate are chosen as the central building block and end group, respectively. Introduction of fused ring to the small molecule enhances the conjugation length of the main chain, and gives a strong tendency to form π–π stacking with a large overlapping area which favors to high charge carrier transport. Small‐molecule organic solar cells based on blends of DCATT and fullerene acceptor exhibit power conversion efficiencies as high as 5.20 % under the illumination of AM 1.5G, 100 mW cm^?2.     

Synthesis and Characterization of Diketopyrrolopyrrole‐based D‐π‐A‐π‐D Small Molecules for Organic Solar Cell Applications

Four new small molecules – CTDP , BCTDP , CFDP , and BCFDP having D‐π‐A‐π‐D molecular architecture, possessing carbazole and benzocarbazole as electron donors, diketopyrrolopyrrole core as acceptor and thiophene/furan acting as spacer/bridge between donor (carbazole and benzocarbazole) and acceptor (diketopyrrolopyrrole) units are synthesized. All the four compounds exhibited absorption in the range of 300 to 700 nm, and, in particular, more intense absorption found in the 500 to 660 nm region. The estimated band gaps are found to be 1.92 eV for CTDP, 1.92 eV for BCTDP, 1.94 eV for CFDP, and 1.92 eV for BCFDP from their intersection point of absorption and emission spectra. The electrochemical studies revealed that the highest occupied molecular orbital/lowest unoccupied molecular orbital energy levels of all the four compounds, CTDP (−5.03/−3.65 eV), BCTDP (−5.03/−3.65 eV), CFDP (−4.94/−3.65 eV), and BCFDP (−4.90/−3.62 eV) are well matched with PCBM and expected to be act as donor materials in small molecule bulk hetero junction organic solar cells. All the compounds are thermally stable up to 382–416°C.     

Highly Efficient Luminescent Solar Concentrators Based on Benzoheterodiazole Dyes with Large Stokes Shifts

Five extended π-conjugated systems with electron donor (D) and acceptor (A) moieties have been synthesized. Their basic D-A-D structural motif is a benzothiadiazole unit symmetrically equipped with two thiophene rings ( S2T ). Its variants include 1) the same molecular framework in which sulfur is replaced by selenium ( Se2T ), also with four thiophene units ( Se4T ) and 2) a D’-D-A-D system having a N-carbazole donor moiety at one end ( CS2T ) and a D’-D-A-D-A’ array with a further acceptor carbonyl unit at the other extremity ( CS2TCHO ). The goal is taking advantage of the intense luminescence and large Stokes shifts of the five molecules for use in luminescent solar concentrators (LSCs). All of them exhibit intense absorption spectra in the UV/Vis region down to 630 nm, which are fully rationalized by DFT. Emission properties have been studied in CH₂Cl₂ (298 and 77 K) as well as in PMMA and PDMS matrices, measuring photoluminescence quantum yields (up to 98 %) and other key optical parameters. The dye–PMMA systems show performances comparable to the present state-of-the-art, in terms of optical and external quantum efficiencies (OQE=47.6 % and EQE=31.3 %, respectively) and flux gain (F=10.3), with geometric gain close to 90. LSC devices have been fabricated and tested in which the five emitters are embedded in PDMS and their wave-guided VIS luminescence feeds crystalline silicon solar cells.     

Theoretical characterization and design of small molecule donor material containing naphthodithiophene central unit for efficient organic solar cells

To seek for high‐performance small molecule donor materials used in heterojunction solar cell, six acceptor–donor–acceptor small molecules based on naphtho[2,3‐b:6,7‐b′]dithiophene ( NDT ) units with different acceptor units were designed and characterized using density functional theory and time‐dependent density functional theory. Their geometries, electronic structures, photophysical, and charge transport properties have been scrutinized comparing with the reported donor material NDT(TDPP)₂ ( TDPP = thiophene‐capped diketopyrrolopyrrole). The open circuit voltage (V_oc), energetic driving force(ΔE_L‐L), and exciton binding energy (E_b) were also provided to give an elementary understanding on their cell performance. The results reveal that the frontier molecular orbitals of 3–7 match well with the acceptor material PC₆₁BM , and compounds 3–5 were found to exhibit the comparable performances to 1 and show promising potential in organic solar cells. In particular, comparing with 1 , system 7 with naphthobisthiadiazole acceptor unit displays broader absorption spectrum, higher V_oc, lower E_b, and similar carrier mobility. An in‐depth insight into the nature of the involved excited states based on transition density matrix and charge density difference indicates that all S₁ states are mainly intramolecular charge transfer states with the charge transfer from central NDT unit to bilateral acceptor units, and also imply that the exciton of 7 can be dissociated easily due to its large extent of the charge transfer. In a word, 7 maybe superior to 1 and may act as a promising donor candidate for organic solar cell. © 2013 Wiley Periodicals, Inc.     

Synthesis and photovoltaic properties of low‐bandgap 4,7‐dithien‐2‐yl‐2,1,3‐benzothiadiazole‐based poly(heteroarylenevinylene)s

Three novel low‐bandgap copolymers containing alkylated 4,7‐dithien‐2‐yl‐2,1,3‐benzothiadiazole (HBT) and different electron‐rich functional groups (dialkylfluorene (PFV‐HBT), dialkyloxyphenylene (PPV‐HBT) and dialkylthiophene (PTV‐HBT)) were prepared by Horner polycondensation reactions and characterized by ¹H NMR, gel permeation chromatography, and elemental analysis. The alkyl side chain brings these polymeric materials good solubility in common organic solvents, which is critical for the manufacture of solar cells in a cost‐effective manner. The copolymers exhibit low optical bandgap from 1.48 to 1.83 eV. The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels of the copolymers were measured by cyclic voltammetry. Theoretical calculations revealed that the variation laws of HOMO and the LUMO energy levels are well consistent with cyclic voltammetry measurement. The bulk heterojunction photovoltaic devices with the structure of ITO/PEDOT‐PSS/polymer:PCBM/LiF/Al were fabricated by using the three copolymers as the donor and (6,6)‐phenyl‐C₆₁‐butyric acid methyl ester (PCBM) as the acceptor in the active layer. The device based on PTV‐HBT:PCBM (1:4 w/w) achieved a power conversion efficiency of 1.05% under the illumination of AM 1.5, 100 mW/cm². © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011.     

Design and synthesis of pyromellitic diimide‐based donor–acceptor conjugated polymers for photovoltaic application

Three of conjugated polymers based on pyromellitic diimide (PMDI) as the acceptor unit and thienothiophene (TT) as the donor unit were successfully synthesized by Stille coupling. The effect of the side chain length and thiophene π‐bridge on the polymers' optical and electrochemical properties was investigated. Electrochemical characterization indicated that these polymers have deep highest occupied molecular orbital energy levels between ?5.7 and ?5.8 eV. Polymer solar cells were fabricated by using these PMDI‐based polymers as the donor and [6,6]‐phenyl‐C61‐butyric acid methyl ester as the acceptor. The polymer P1 whose PMDI unit was functionalized with 2‐ethylhexyl side chain shows the higher short‐circuit current (J_sc) and fill factor (FF) compared with that of P2 with a 2‐octyldodecyl side chain on the PMDI unit. The results also illustrate that the insertion of a thiophene π‐bridge between PMDI and TT (the polymer P3) leads to the broader absorption and better photovoltaic performance. The best performance was obtained from the cell based on the polymer P3 with a power conversion efficiency of 0.43% under the illumination of AM 1.5 G, 100 mW/cm². Copyright © 2014 John Wiley & Sons, Ltd.