基于PCPDTBT复合材料的制备及光致电荷转移

合成了PCPDTBT,通过NMR,GPC等方法对聚合物进行了表征.研究了聚合物的热学与电化学性质.采用溶液法将电子给体PCPDTBT与两种电子受体1-(3-甲氧基羰基)丙基-1-苯基[6,6]C61(PCBM)和ZnO纳米粒子分别进行了复合,通过研究复合前后的荧光变化,确认了给体-受体两相界面间发生了由分子能级差引发的光致电荷转移.这些研究结果为探索性能更佳的有机太阳能电池材料体系提供了重要的参考依据.     

A three-step synthetic approach to asymmetrically functionalized 4H-cyclopenta[2,1-b:3,4-b']dithiophenes

A convenient and efficient three-step route toward both symmetrically and asymmetrically functionalized 4H-cyclopenta[2,1-b:3,4-b']dithiophenes has been developed. Using this method a broad collection of functionalized bridged bithiophenes can smoothly be accessed. Starting from 3-bromo-2,2'-bithiophene, prepared by Kumada coupling of 2-thienylmagnesium bromide with 2,3-dibromothiophene under Pd(dppf)Cl(2) catalysis, lithiation and subsequent reaction with dialkyl ketones afforded (a)symmetrically dialkylated tertiary alcohol derivatives. By means of final Friedel-Crafts dehydration cyclization in sulfuric acid medium, these derivatives were converted to 4,4-dialkyl-4H-cyclopenta[2,1-b:3,4-b']dithiophenes. Upon replacement of the dialkyl ketone reagent by ethyl levulinate, an ester-functionalized 4H-cyclopenta[2,1-b:3,4-b']dithiophene was prepared, representing an attractive precursor for variously functionalized cyclopentadithiophene compounds.     

Engineering organic sensitizers for iodine-free dye-sensitized solar cells: red-shifted current response concomitant with attenuated charge recombination

With a new metal-free donor-acceptor photosensitizer featuring the 2,6-bis(thiophen-2-yl)-4,4-dihexyl-4H-cyclopenta[2,1-b:3,4-b']dithiophene-conjugated spacer and the tris(1,10-phenanthroline)cobalt(II/III) redox shuttle, we present a highly efficient iodine-free dye-sensitized solar cell displaying a power conversion efficiency of 9.4% measured at 100 mW cm(-2) simulated AM1.5 conditions.     

Fine-tuning the Electronic Structure of Organic Dyes for Dye-Sensitized Solar Cells

A series of metal-free organic dyes exploiting different combinations of (hetero)cyclic linkers (benzene, thiophene, and thiazole) and bridges (4H-cyclopenta[2,1-b:3,4-b']dithiophene (CPDT) and benzodithiophene (BDT)) as the central π-spacers were synthesized and characterized. Among them, the sensitizer containing the thiophene and CPDT showed the most broad incident photon-to-current conversion efficiency spectra, resulting in a solar energy conversion efficiency (η) of 6.6%.     

低聚合度的交替共聚物太阳能电池的形态和性能

制备了由低聚合度的聚[2,6-(4,4-双-(2-乙基己基)-4H-环戊[2,1-b;3,4-b']双噻吩)-交替-4,7-(2,1,3-苯并噻二唑)](LDP-PCPDTBT)、[6,6]-苯基-C61-丁酸甲酯(PC61BM)和聚甲基丙烯酸甲酯(PMMA)组成的三组分共混薄膜,并通过加入溶剂添加剂(1,8-二溴辛烷,DBO)对体系进行了优化处理.研究发现,没有加入DBO时,LDP-PCPDTBT和PC61BM相在PMMA的基质中分别是无定形的和结晶的;加入DBO后,PMMA基质中LDP-PCPDTBT和PC61BM间的相分离过程得到优化,有机太阳能电池的能量转换效率相应提高了32.4%.     

Synthesis, solid state structure and polymerisation of a fully planar cyclopentadithiophene

The new fully planar cyclopentadithiophene, 4-n-dodecylidene-4H-cyclopenta(2,1-b;3,4-b')dithiophene, shows extensive pi-stacking in the solid state with short intermolecular distances (ca. 3.5 A) between adjacent molecules. Polymerisation of this monomer by two different protocols gave solution processable alkenyl-bridged cyclopentadithiophene polymers with extended pi-conjugation in the main chain.     

小分子优先结晶构筑聚合物/非富勒烯共混体系互穿网络结构

非富勒烯小分子受体(SMAs)有序聚集决定聚合物/非富勒烯共混体系光伏电池的双分子复合几率。 然而,由于非对称相分离聚合物趋于优先形成网络,抑制小分子受体分子结晶。 在聚[(2,6-(4,8-二(5-(2-乙基己基噻吩-2-基)苯并[1,2-b:4,5-b']二噻吩))-alt-(5,5-(1',3'-二-2-噻吩基-5',7'-二(2-乙基己基)苯并[1',2'-c:4',5'-c']二噻吩-4,8-二酮))](PBDB-T)/9-二(2-亚甲基(3-(1,1-二氰基亚甲基)-6,7-二氟-茚酮))-5,5,11,11-四(4-己基苯基)-二噻吩并[2,3-d:2',3'-d']-s-引达省[1,2-b:5,6-b']二噻吩(IT-4F)共混体系,四氢呋喃蒸汽处理可提高IT-4F结晶性,150 ℃热退火可提高PBDB-T的结晶性。 因此,依次利用蒸汽退火和热退火处理薄膜,诱导小分子先结晶、聚合物后结晶,从而降低PBDB-T对小分子扩散的限制,构建高结晶互穿网络结构。 形貌优化后降低了双分子复合,器件光电转换效率从5.95%提高至7.18%。     

Effects of substituted side‐chain position on donor–acceptor conjugated copolymers

The optical properties and electrical properties of a series of low‐band‐gap conjugated copolymers, in which alkyl side chains were substituted at various positions, were investigated using donor–acceptor conjugated copolymers consisting of a cyclopentadithiophene derivative and dithienyl‐benzothiadiazole. With substituted side chains, the intrinsic properties of the copolymers were significantly altered by perturbations of the intramolecular charge transfer. The absorption of poly[2, 6‐(4,4‐bis(2‐octyl)‐4H‐cyclopenta‐[2,1‐b:3,4‐b′]dithiophene)‐alt‐4, 7‐bis(4‐octyl‐thiophene‐2‐yl)benzo‐2,1,3‐thiadiazole] [ PCPDT‐ttOTBTOT ( P2 )], which assumed a tail–tail configuration, tended to blue shift relative to the absorption of poly[2,6‐(4,4‐bis(2‐octyl)‐4H‐cyclopenta‐[2,1‐b:3,4‐b′]dithiophene)‐alt‐4,7‐bis (thiophene‐2‐yl)benzo‐2,1,3‐thiadiazole] [ PCPDT‐TBTT ( P1 )]. The absorption of poly[2,6‐(4,4‐bis(2‐octyl)‐4H‐cyclopenta‐[2,1‐b:3, 4‐b′]dithiophene)‐alt‐4,7‐bis(3‐octyl‐thiophene‐2‐yl)benzo‐2,1,3‐thiadiazole] [ PCPDT‐hhOTBTOT ( P3 )], which assumed a head–head configuration, was blue shifted relative to that of P2 . The electrical transport properties of field‐effect transistors were sensitive to the side chain position. The field‐effect mobility in P2 (μ₂ = 1.8 × 10^?3 cm²/V s) was slightly lower than that in P1 (μ₁ = 4.9 × 10^?3 cm²/V s). However, the mobility of P3 was very low (μ₃ = 3.8 × 10^?6 cm²/V s). Photoexcitation spectroscopy showed that the charge generation efficiency (shown in transient absorption spectra) and polaron pair mobility in P1 and P2 were higher than in P3 , yielding P1 and P2 device performances that were better than the performance of devices based on P3 . © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Ultrahigh mobility in polymer field-effect transistors by design

In this article, the design paradigm involving molecular weight, alkyl substituents, and donor-acceptor interaction for the poly[2,6-(4,4-bis-alkyl-4H-cyclopenta[2,1-b;3,4-b']-dithiophene)-alt-4,7-(2,1,3-benzothiadiazole)] (cyclopentadithiophene-benzothiadiazole) donor-acceptor copolymer (CDT-BTZ) toward field-effect transistors (FETs) with ultrahigh mobilities is presented and discussed. It is shown that the molecular weight plays a key role in improving hole mobilities, reaching an exceptionally high value of up to 3.3 cm(2) V(-1) s(-1). Possible explanations for this observation is highlighted in conjunction with thin film morphology and crystallinity. Hereby, it is found that the former does not change, whereas, at the same time, crystallinity improved with ever growing molecular weight. Furthermore, other important structural design factors such as alkyl chain substituents and donor-acceptor interaction between the polymer backbones potentially govern intermolecular stacking distances crucial for charge transport and hence for device performance. In this aspect, for the first time we attempt to shed light onto donor-acceptor interactions between neighboring polymer chains with the help of solid state nuclear magnetic resonance (NMR). On the basis of our results, polymer design principles are inferred that might be of relevance for prospective semiconductors exhibiting hole mobilities even exceeding 3 cm(2) V(-1) s(-1).     

Synthesis and photovoltaic properties of new donor-acceptor benzodithiophene-containing copolymers

Four new alternating narrow band-gap copolymers containing benzodithiophene, 4,8-dithiophen-2-yl-benzo[1,2-c;4,5-c′-bis[1,2,5]thiadiazole, 4,9-bis(thiophen-2-yl)-6,7-di(2-ethylhexyl)-[1,2,5]thiadiazolo[3,4-g]quinoxaline, 5,8-dibromo-2,3-bis(5-octylthiophen-2-yl)quinoxaline, and 4,7-bis(5-bromothiophen-2-yl)benzo[1,2,5] thiadiazole units are synthesized under Stille reaction conditions. The structures, molecular masses, and physical properties of the copolymers are studied via ¹H NMR spectroscopy, GPC, cyclic voltammetry, and thermomechanical and thermogravimetric analyses. The polymers show solubility and a broad absorption region (with the band gap in the range from 0.81 to 1.53 eV). All of the polymers are photostable in air, and their levels of the highest occupied molecular orbital vary from ?4.98 to ?5.30 eV. Polymer solar cells based on these copolymers as donors and fullerene PC₆₀BM as an acceptor show open-circuit voltages in the range 0.16–0.61 V, and the efficiencies of the devices are in the range 0.02–0.49%.     

Polymer solar cells with an inverted device configuration using polyhedral oligomeric silsesquioxane-[60]fullerene dyad as a novel electron acceptor

A polyhedral oligomeric silsesquioxane-[60]fullerene (POSS-C60) dyad was designed and used as a novel electron acceptor for bulk heterojunction (BHJ) polymer solar cells (PSCs) with an inverted device configuration. The studies of time-resolved photoinduced absorption of the pristine thin film of poly[(4,4’-bis(2-ethylhexyl)dithieno[3,2-b:2’,3’-d]silole)-2,6-diyl-alt-(4,7-bis (2-thienyl)-2,1,3-benzothiadiazole)-5,5’-diyl] (SiPCPDTBT) and the composite thin film of SiPCPDTBT:POSS-C60 indicated efficient electron transfer from SiPCPDTBT to POSS-C60 with inhibited back-transfer. BHJ PSCs made by SiPCPDTBT mixed with POSS-C60 yielded the power conversion efficiencies (PCEs) of 1.50%. Under the same operational conditions, PCEs observed from BHJ PSCs made by SiPCPDTBT mixed with [6,6]-phenyl-C61-butyric acid methyl ester were 0.92%. These results demonstrated that POSS-C60 is a potentially good electron acceptor for inverted BHJ PSCs.     

Effects of various donor: acceptor blend ratios on photophysical properties in non-fullerene organic bulk heterojunctions

In this work, the donor:acceptor ratio effected photophysical properties of non-fullerene organic solar cells are comparatively investigated. Effective transportation of the photo-generated charge carriers can be obtained with the PDBD-T:ITIC ratio variation. There is no significant energy loss variation exists in the process of changing the D:A ratio.     

Synthesis and characterization of [1,2,5]chalcogenazolo[3,4-f]benzo[1,2,3]triazole and [1,2,3]triazolo[3,4-g]quinoxaline derivatives

The synthesis and characterization is reported of low bandgap [1,2,5]chalcogenazolo[3,4-f]benzo[1,2,3]triazole and [1,2,3]triazolo[3,4-g]quinoxaline derivatives that display higher solubility and stability then their thiadiazole counterparts, [1,2,5]chalcogenazolo[3,4-f]benzo[2,1,3]thiadiazole and [1,2,5]thiadiazolo[3,4-g]quinoxaline, respectively.     

All-polymer solar cells with perylenediimide polymer acceptors

Four polymers based on perylenediimide co-polymerized with thiophene, bithiophene, selenophone and thieno[3,2-b]thiophene were investigated as the acceptor materials in all-polymer solar cells. Two different donor polymers, poly[4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b;4,5-b′]dithiophene-2,6-diyl-alt-(4-(2-ethylhexyl)-3-fluorothieno[3,4-b]thiophene)-2-carboxylate-2,6-diyl](PTB7-Th) and poly[(5,6-difluoro-2,1,3-benzothiadiazol-4,7-diyl)-alt-(3,3′′′-di(2-dodecyltetradecyl)-2,2′;5′,2″;5″,2′′′-quaterthiophen-5,5′′′-diyl)](Pff BT4T-2DT), with suitably complementary absorption spectra and energy levels were applied and examined. Among all different donor-acceptor pairs studied here, the combination of PTB7-Th:poly[N,N′-bis(1-hexylheptyl)-3,4,9,10-perylenediimide-1,6/1,7-diyl-alt-2,5-thiophene](PDI-Th) exhibited the best power conversion efficiency(PCE) of 5.13%, with open-circuit voltage(V_(oc)) = 0.79 V, short-circuit current density(J_(sc)) = 12.35 mA·cm~(-2) and fill-factor(FF) = 0.52. The polymer of PDI-Th acceptor used here had a regio-irregular backbone, conveniently prepared from a mixture of 1,6- and 1,7-dibromo-PDI. It is also noteworthy that neither additive nor posttreatment is required for obtaining such a cell performance.     

含苯并硒二唑聚咔唑/芴类共轭聚电解质及其前驱体的合成与性能研究

采用Suzuki偶合反应合成了一系列新型的咔唑、芴和2,1,3-苯并硒二唑的共聚物——聚[3,6-(N-(2-乙基己基))咔唑-2,1,3-苯并硒二唑-9,9-双(N,N-二甲基胺丙基)芴](PCzN-BSeD)及其相应的聚电解质衍生物——聚[3,6-(N-(2-乙基己基))咔唑-2,1,3-苯并硒二唑-9,9-(双(3′-(N,N-二甲基)-N-乙基铵)丙基)芴]二溴(PCzNBr-BSeD).在聚咔唑和芴中引入不同比例的2,1,3-苯并硒二唑(BSeD)单元,引起了由咔唑和芴链段向窄带隙苯并硒二唑(BSeD)单元有效的能量转移.通过对聚合物电致发光性能的研究,发现用聚(3,4-亚乙基二氧基噻吩)(PEDOT)或聚(3,4-亚乙基二氧基噻吩)/聚乙烯咔唑(PEDOT/PVK)作为空穴传输层时,器件的性能相差不大,表明咔唑的引入较明显的改善了聚合物的空穴注入性能.而且几乎所有的聚合物用高功函数铝作阴极的器件和用钡/铝作阴极的器件具有相近的发光性能,表明这类聚合物具有良好的电子注入性能.     

Linear- and angular-shaped naphthodithiophenes: selective synthesis, properties, and application to organic field-effect transistors

A straightforward synthetic approach that exploits linear- and angular-shaped naphthodithiophenes (NDTs) being potential as new core structures for organic semiconductors is described. The newly established synthetic procedure involves two important steps; one is the chemoselective Sonogashira coupling reaction on the trifluoromethanesulfonyloxy site over the bromine site enabling selective formation of o-bromoethynylbenzene substructures on the naphthalene core, and the other is a facile ring closing reaction of fused-thiophene rings from the o-bromoethynylbenzene substructures. As a result, three isomeric NDTs, naphtho[2,3-b:6,7-b']dithiophene, naphtho[2,3-b:7,6-b']dithiophenes, and naphtho[2,1-b:6,5-b']dithiophene, are selectively synthesized. Electrochemical and optical measurements of the parent NDTs indicated that the shape of the molecules plays an important role in determining the electronic structure of the compounds; the linear-shaped NDTs formally isoelectronic with naphthacene have lower oxidation potentials and more red-shifted absorption bands than those of the angular-shaped NDTs isoelectronic with chrysene. On the contrary, the performance of the thin-film-based field-effect transistors (FETs) using the dioctyl or diphenyl derivatives were much influenced by the symmetry of the molecules; centrosymmetric derivatives tend to give higher mobility (up to 1.5 cm(2) V(-1) s(-1)) than axisymmetric ones (～0.06 cm(2) V(-1) s(-1)), implying that the intermolecular orbital overlap in the solid state is influenced by the symmetry of the molecules. These results indicate that the present NDT cores, in particular the linear-shaped, centrosymmetric naphtho[2,3-b:6,7-b']dithiophene, are promising building blocks for the development of organic semiconducting materials.     

Donor-acceptor (D-A) terpolymers based on alkyl-DPP and t-BocDPP moieties for polymer solar cells

A series of low band gap terpolymers based on 4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b¢] dithiophene (BDTT) and diketopyrrolopyrrole (DPP) with varied solubilizing groups (i.e., tert-butoxycarbonyl, t-Boc and 2-octyldodecyl) are developed as electron donors for bulk heterojunction (BHJ) polymer solar cells (PSCs). The results reveal that the one with 50% t-Boc concentration (P3) performs better than the other terpolymers used in this study in conventional PSC devices with a power conversion efficiency of 2.92%.     

Synthesis and properties of thiophene-fused benzocarborane

The o-carborane-based π-conjugated compound, benzocarborano- [2,1-b:3,4-b']dithiophene was synthesized. Its crystal structure revealed high coplanarity for the two thiophene rings of the 2,2'-bithiophene skeleton, which is fixed in the cisoid structure by the o-carborane unit. Theoretical calculations indicated non-aromaticity for its center C(6) ring moiety as well as decreased HOMO and LUMO levels. The o-carborane moiety provides an electron-withdrawing character to the 2,2'-bithiophene unit through an inductive effect.     

First Principles Probing of Photo-Generated Intermolecular Charge Transfer State in Conjugated Oligomers

We perform density functional theory calculations to investigate the polaron pair (charge transfer state) photo-generation in donor-acceptor oligomer methyl-capped (4, 7-benzo[2, 1, 3]thiadiazole-2, 6-(4, 4-bis (2-ethylhexyl)-4H-cyclopenta[1, 2-b; 3, 4-b']dithiophene-4, 7-benzo[2, 1, 3]thiadiazole)(CPDTBT).Results show that effective photo-generation of charge transfer state can happen in CPDTBT dimer when the group 4, 7-benzo[2, 1, 3]thiadiazole (BT) in one monomer deviates against the conjugated plane (onset torsion angle is about 20°).The lower excitation energy (530 nm) can only generate the intramolecular excitonic state, while the higher excitation energy (370 nm) can generate the intermolecular charge transfer state, in good agreement with the experiment.Moreover, the mechanism of charge separation in CPDTBT oligomers is discussed.     

Chlorine-Substituted N-Heteroacene Analogues Acting as Organic Semiconductors for Solution-Processed n-type Organic Field-Effect Transistors

High performance solution processable n-type organic semiconductor is an essential element to realize low-cost, all organic and flexible composite logic circuits. In the design of n-type semiconducting materials, tuning the LUMO level of compounds is a key point. As a strong electron withdrawing unit, the introduction of chlorine atom into the chemical structure can increase the electron affinity of the material and reduce the LUMO energy level. Here, a series chlorine substituted N-heteroacene analogues of 6,7,8,9-tetrachloro-4,11-bis(4-((2-ethylhexyl)oxy)phenyl)-[1,2,5]thiadiazolo[3,4-b]phenazine (O4Cl), 6,7,8,9-tetrachloro-4,11-bis(4-((2-ethylhexyl)thio)phenyl)-[1,2,5]thiadiazolo[3,4-b]phenazine (S4Cl), 1,2,3,4,8,9,10,11-octachloro-6,13-bis(4-((2-ethylhexyl)oxy)phenyl)quinoxalino[2,3-b]phenazine (8Cl) and 12Cl have been synthesized and characterized. Solution-processed organic field-effect transistors (OFETs) based on these four compounds exhibit good electron mobilities of 0.04 cm² V⁻¹ s⁻¹, 0.01 cm² V⁻¹ s⁻¹, 2×10⁻³ cm² V⁻¹ s⁻¹ and 3×10⁻³ cm² V⁻¹ s⁻¹, respectively, under ambient conditions. The results suggest that these chlorine substituted π-conjugated N-heteroacene analogues are promising n-type semiconductors in OFET applications.