Amorphous molecular material containing bisthiophenyl-benzothiadiazole and triphenylamine with bipolar and low-bandgap characteristics for solar cells

He, Qingguo; He, Chang; Sun, Yuxi; Wu, Hongxia; Li, Yongfang; Bai, Fenglian

doi:10.1016/j.tsf.2007.10.058

Cited by 23 publications

(14 citation statements)

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“…The poor ll factors also hint towards unbalanced charge transport, which is likely attributed to the limited mobility of azomethines when processed under these conditions. The vinyl analogues of TPA-Th-TPA and TPA-TBT-TPA have been published by other groups and show PCEs of 0.34% and 0.26%, respectively aer optimization, 12,15,16 which is signicantly lower than 1.21% and 1.15% found for the azomethine analogues published herein. Also a TPA-TBT-TPA analogue where the TPA moieties are directly connected to the TBT core without a vinyl or azomethine bond has been published and reached a PCE of 1.3% aer extensive device optimization using [70]PCBM, which is only slightly higher compared to the azomethine we report.…”

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confidence: 42%

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Small-molecule azomethines: organic photovoltaics via Schiff base condensation chemistry

et al. 2014

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Conjugated small-molecule azomethines for photovoltaic applications were prepared via Schiff base condensation chemistry. Bulk heterojunction (BHJ) devices exhibit efficiencies of 1.2% with MoO x as the hole-transporting layer. The versatility and simplicity of the chemistry is illustrated by preparing a photovoltaic device directly from the reaction mixture without any form of workup.Most of the conjugated materials used in organic electronics are synthesized using time-consuming Suzuki-, Wittig-, or Hecktype coupling reactions. These chemistries oen make use of expensive transition metal catalysts, require stringent reaction conditions, and extensive product purication.In order to offer a more economic route towards organic photovoltaic materials we are currently exploring azomethines (-CH]N-) as the conjugated linker unit. The azomethine bond is isoelectronic to the vinyl bond and possesses similar optoelectronic and thermal properties. [1][2][3][4] Besides that, azomethines offer signicant advantages over vinylenes as they can be prepared using Schiff base condensation chemistry under near ambient reaction conditions. Expensive catalysts are not required and water is the only by-product. The reported conjugated poly(azomethine)s are only moderately soluble and therefore difficult to process. 8,9 Small-molecules, on the other hand, have the advantage of having a higher solubility, a well-dened molecular structure, and no batch-to-batch variations. Recent results have shown that conjugated small molecules can compete successfully with their polymeric counterparts. 10,11For this study we have synthesized two azomethine-based small molecules via a simple condensation reaction (Fig. 1).4-Aminotriphenylamine (TPA, 1) was reacted with two conjugated dialdehydes. 2,5-Thiophenedicarbaldehyde (Th, 2a) was used since thiophenes have been studied extensively and possess good charge transport properties.12 Besides that, both materials are readily available from commercial sources. 4,7-Bis(5-formylthiophen-2-yl)-2,1,3-benzothiadiazole (TBT, 2b) was used because it is a strong electron-accepting moiety and this yields a bipolar donor-acceptor-donor molecule with a small bandgap and thus a larger overlap with the solar spectrum.13 In addition TBT is known to possess high mobilities and good lm-forming abilities.14,15 The reaction was performed in chloroform and p-toluenesulfonic acid was used as a catalyst. The products (3a,b) were precipitated, and treated with diluted triethylamine to neutralize the protonated azomethine bond. The small molecules were obtained in good yields (>80%) and characterized using 1 H and 13 C NMR, FTIR, and mass spectrometry where possible. Detailed synthetic procedures and characterization of the small molecules and their intermediates are available in the ESI. † The thermal properties of the new molecules were assessed using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Both small molecules show excellent This journal is

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confidence: 42%

“…The azomethine moiety slightly deepens the HOMO energy level compared to the vinyl and fully aromatic analogues, which are about 0.1-0.3 eV higher. 12,15 This is attributed to the electron-withdrawing nature of the azomethine functionality.…”

Section: 17mentioning

confidence: 99%

Small-molecule azomethines: organic photovoltaics via Schiff base condensation chemistry

et al. 2014

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“…6 was synthesized by further bromination [of 5] (check in scheme) with N-bromosuccinimide (NBS), [46] while 7 was synthesized via a Heck reaction with a controlled feeding ratio of N,N-diphenyl-4-vinylbenzenamine to 3. [47] TBT and TBBBT were synthesized by Suzuki coupling between 1 and 4 or 1 and 7, and obtained in yields of 53.6% or 65.6%, respectively. BBB and BTBTB were synthesized by Suzuki coupling between 2 and 3 or 2 and 6, and obtained in yields of 32% or 59%, respectively.…”

Section: Synthesismentioning

confidence: 99%

Binaphthyl‐Containing Green‐ and Red‐Emitting Molecules for Solution‐Processable Organic Light‐Emitting Diodes

Zhou

Yang

et al. 2008

Adv Funct Materials

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111

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Strong intermolecular interactions usually result in decreases in solubility and fluorescence efficiency of organic molecules. Therefore, amorphous materials are highly pursued when designing solution‐processable, electroluminescent organic molecules. In this paper, a non‐planar binaphthyl moiety is presented as a way of reducing intermolecular interactions and four binaphthyl‐containing molecules (BNCMs): green‐emitting BBB and TBT as well as red‐emitting BTBTB and TBBBT, are designed and synthesized. The photophysical and electrochemical properties of the molecules are systematically investigated and it is found that TBT, TBBBT, and BTBTB solutions show high photoluminescence (PL) quantum efficiencies of 0.41, 0.54, and 0.48, respectively. Based on the good solubility and amorphous film‐forming ability of the synthesized BNCMs, double‐layer structured organic light‐emitting diodes (OLEDs) with BNCMs as emitting layer and poly(N‐vinylcarbazole) (PVK) or a blend of poly[N,N′‐bis(4‐butylphenyl)‐N,N′‐bis(phenyl)benzidine] and PVK as hole‐transporting layer are fabricated by a simple solution spin‐coating procedure. Amongst those, the BTBTB based OLED, for example, reaches a high maximum luminance of 8315 cd · m−2 and a maximum luminous efficiency of 1.95 cd · A−1 at a low turn‐on voltage of 2.2 V. This is one of the best performances of a spin‐coated OLED reported so far. In addition, by doping the green and red BNCMs into a blue‐emitting host material poly(9,9‐dioctylfluorene‐2,7‐diyl) high performance white light‐emitting diodes with pure white light emission and a maximum luminance of 4000 cd · m−2 are realized.

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“…The HOMO/LUMO energy levels and the charge mobility of new p-type materials should also be optimized as these properties are intimately related to photovoltaic performance, as proposed by Scharber et al 6 Benzothiadiazole (BT) is a well-known electron-deficient molecule which can be conjugated with an electron-rich molecule to form oligomers or polymers with small band gap energies, 7,8 and several different polymers of this variety have been synthesized for applications in electronic devices. 9,10 Recently, Heeger and coworkers used a polymer of alternating cyclopentadithiophene and dibenzothiadiazole units in the fabrication of photovoltaic cells, yielding a PCE of 5%. …”

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confidence: 99%

“…9,10 Recently, Heeger and coworkers used a polymer of alternating cyclopentadithiophene and dibenzothiadiazole units in the fabrication of photovoltaic cells, yielding a PCE of 5%. 11 Carbazole derivatives have a planar conjugated structure and good hole transporting properties as well as electron-donating properties.…”

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confidence: 99%

A Thiophene, Benzothiadiazole, and Carbazole-Based Copolymer : Synthesis and Characterization

Li¹,

Meng²,

Kim³

et al. 2009

Bulletin of the Korean Chemical Society

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Of the various types of polymerbased, photovoltaic devices designed to date, the most efficient photovoltaic devices, having power conversion efficiencies (PCEs) of 3-4%, were fabricated using a blend of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) as the electron-donor and electron-acceptor materials, respectively.1,2 Soon after the initial reports, P3HT/PCBM-based photovoltaic devices were optimized to achieve PCEs approaching 5%.3-5 New p-type polymers, which absorb light more broadly in the terrestrial solar radiation spectrum, were needed to increase the PCE of these photovoltaic devices. The HOMO/LUMO energy levels and the charge mobility of new p-type materials should also be optimized as these properties are intimately related to photovoltaic performance, as proposed by Scharber et al. 6 Benzothiadiazole (BT) is a well-known electron-deficient molecule which can be conjugated with an electron-rich molecule to form oligomers or polymers with small band gap energies, 7,8 and several different polymers of this variety have been synthesized for applications in electronic devices. 9,10 Recently, Heeger and coworkers used a polymer of alternating cyclopentadithiophene and dibenzothiadiazole units in the fabrication of photovoltaic cells, yielding a PCE of 5%. 11Carbazole derivatives have a planar conjugated structure and good hole transporting properties as well as electron-donating properties.12 Blouin and coworkers have synthesized copolymers bearing carbazole units and employed them in the fabrication of photovoltaic devices with PCEs reaching to 3.6%. 13It appeared interesting to study polymers bearing thiophene-carbazole derivatives and BT as electron-releasing and electron-withdrawing units, respectively, in a polymer backbone. Thus, the goal of this report is to report the synthesis of a conjugated polymer consisting of 3HT, BT, and 2-ethylhexylcarbazol (CZ) (P3HT2BTCZ) and describe the optical and electrochemical properties of the resulting polymer. Experimental SectionMaterials. 3-Hexylthiophene (3HT), carbazole, 2,1,3-benzothiadiazole, n-butyllithium (2.5 M in hexane), 2-isopropoxy-4,4,5,5-tetramethyl-1,3,2-dioxaborolane, tributyltin chloride, tetrakis(triphenylphosphine) palladium(0), tetrahydrofuran (THF), N-bromosuccinimide (NBS), potassium carbonate, bromine, hydrogen bromide, toluene, and chloroform were purchased from Aldrich and used without further purification. 4,7-Bis(5-bromo-4-hexylthiophene-2-yl)benzo[c][1,2,5]-thiadiazole (1).The synthetic procedure of compound 1 has been described elsewhere 14 (orange solid, 0.51 g, 85% yield). 3,6-Dibromocarbazole (2). Using a modified version of a previously reported method, 15 carbazole (16.7 g, 100 mmol) was dissolved in DMF (150 mL) at 0 o C with stirring, followed by the addition of a solution of NBS (36.3 g, 200 mmol) in 100 mL of DMF. The resulting mixture was stirred at room temperature for 2 hr, and the solution then poured into 1 L of water, filtered, and washed with water. The crude product was rec...

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Amorphous molecular material containing bisthiophenyl-benzothiadiazole and triphenylamine with bipolar and low-bandgap characteristics for solar cells

Cited by 23 publications

References 28 publications

Small-molecule azomethines: organic photovoltaics via Schiff base condensation chemistry

Small-molecule azomethines: organic photovoltaics via Schiff base condensation chemistry

Binaphthyl‐Containing Green‐ and Red‐Emitting Molecules for Solution‐Processable Organic Light‐Emitting Diodes

A Thiophene, Benzothiadiazole, and Carbazole-Based Copolymer : Synthesis and Characterization

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