Poly(benzodithiophene) Homopolymer for High-Performance Polymer Solar Cells with Open-Circuit Voltage of Near 1 V: A Superior Candidate To Substitute for Poly(3-hexylthiophene) as Wide Bandgap Polymer

Kang, Tae Eui; Kim, Taesu; Wang, Cheng; Yoo, Seunghyup; Kim, Bumjoon J.

doi:10.1021/acs.chemmater.5b00481

Cited by 41 publications

(37 citation statements)

References 70 publications

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“…Furthermore, Kim et al reported a new homopolymer PBDTT ( P8 ) with a high absorption coefficient (2.5 × 10 5 cm −1 ): an impressive PCE of 6.12% was achieved without the use of any solvent additive or thermal annealing treatment. Moreover, high J sc and internal quantum efficiency (IQE) values were attained due to the optimized BHJ morphology . Figure 3 summarizes the chemical structures of WBG homopolymers discussed in this article, and their basic optical and electronic properties as well as photovoltaic performances are listed in Table 1 .…”

Section: Wbg Homopolymersmentioning

confidence: 99%

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Recent Advances in Wide‐Bandgap Photovoltaic Polymers

2017

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The past decade has witnessed significant advances in the field of organic solar cells (OSCs). Ongoing improvements in the power conversion efficiency of OSCs have been achieved, which were mainly attributed to the design and synthesis of novel conjugated polymers with different architectures and functional moieties. Among various conjugated polymers, the development of wide-bandgap (WBG) polymers has received less attention than that of low-bandgap and medium-bandgap polymers. Here, we briefly summarize recent advances in WBG polymers and their applications in organic photovoltaic (PV) devices, such as tandem, ternary, and non-fullerene solar cells. Addtionally, we also dissuss the application of high open-circuit voltage tandem solar cells in PV-driven electrochemical water dissociation. We mainly focus on the molecular design strategies, the structure-property correlations, and the photovoltaic performance of these WBG polymers. Finally, we extract empirical regularities and provide invigorating perspectives on the future development of WBG photovoltaic materials.

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Section: Wbg Homopolymersmentioning

confidence: 99%

“…An increased interest in acenes from the academic community was aroused by the discovery of conducting plastics . Since then, the semiconducting properties of conjugated systems have been intensively investigated; moreover, a few acene derivatives have been synthesized thereafter to explore their potential in organic electronics …”

Section: Wbg Homopolymersmentioning

confidence: 99%

Recent Advances in Wide‐Bandgap Photovoltaic Polymers

2017

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“…[ 4 ] However, molecular design and synthesis of high bandgap polymers (bandgap > 1.9 eV), which are essential for tandem solar cells to convert highenergy photons and to provide high voltage in subcells, were not widely investigated. High bandgap copolymers reported so far containing thiophene (P3HT and PBDT2FT), [ 5 ] benzodithiophene (PBDTT), [ 6 ] dithieno[3,2-b :2′,3′-d]pyridin-5(4H)-one (PDTPO-BDTO and PDTPO-BDTT), [ 7 ] benzothiadiazole (PCDTBT and HD-PDFC-DTBT), [ 8 ] fl uorinated benzotriazoles wileyonlinelibrary.com the thiophene moieties (PBDTT-FTAZ) was also synthesized for comparison. BHJ solar cells fabricated from PBDTTS-FTAZ and [6,6]-phenyl C 71 -butyric acid methyl ester (PC 71 BM), optimized by varying the mixing ratio of the blend, exhibited a PCE of 8.1% without any solvent additives and post-annealing treatments.…”

Section: Doi: 101002/aelm201600084mentioning

confidence: 99%

“…High bandgap copolymers reported so far containing thiophene (P3HT and PBDT2FT), [ 5 ] benzodithiophene (PBDTT), [ 6 ] dithieno[3,2-b :2′,3′-d]pyridin-5(4H)-one (PDTPO-BDTO and PDTPO-BDTT), [ 7 ] benzothiadiazole (PCDTBT and HD-PDFC-DTBT), [ 8 ] fl uorinated benzotriazoles wileyonlinelibrary.com the thiophene moieties (PBDTT-FTAZ) was also synthesized for comparison. BHJ solar cells fabricated from PBDTTS-FTAZ and [6,6]-phenyl C 71 -butyric acid methyl ester (PC 71 BM), optimized by varying the mixing ratio of the blend, exhibited a PCE of 8.1% without any solvent additives and post-annealing treatments. After thermal annealing, the PCE was further improved to 8.3%, with V oc of 0.83 V and a FF over 0.70.…”

Section: Doi: 101002/aelm201600084mentioning

confidence: 99%

High Bandgap (1.9 eV) Polymer with Over 8% Efficiency in Bulk Heterojunction Solar Cells

Genene

Wang

Meng

et al. 2016

Adv Elect Materials

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(PBDT-FTAZ), [ 9 ] thieno [3,4-c ]pyrrole-4,6-dione (PBDT-TPD) [ 10 ] and 1,3-bis(thiophen-2-yl)-5,7-bis(2-ethylhexyl)benzo-[1,2-c :4,5-c ′] dithiophene-4,8-dione (PDBT-T1) [ 11 ] showed PCEs not more than 8% in conventional single junction solar cells. Up to now, there are only few high bandgap polymers with PCE over 8% were reported ( Table 1 ). [ 2e , 12 ] In order to further improve the performances of tandem solar cells, high bandgap (>1.9 eV) conjugated polymers with low-lying highest occupied molecular orbitals (HOMOs) amenable to larger open-circuit voltages ( V oc ), and comparably high PCEs (over 8%) in BHJ devices are required. [ 4 ] Recently, the high bandgap copolymer PBDT-FTAZ which consists of alternating units of benzodithiophene (BDT) and fl uorinated benzotriazole (FTAZ) has attracted considerable interest due to the high PCE of 7% and fi ll factor (FF) of over 0.7 in BHJ devices with thick active layers. [ 9 ] It will be very interesting to further improve the photovoltaic performance of this polymer via fi ne-tuning its chemical structure.Donor polymers based on 2D-conjugated BDT units substituted with alkylthiophene side chains have been shown to exhibit high performance with excellent thermal stability, hole mobility, and spectral coverage. [ 13 ] Li and co-workers [ 14 ] attached conjugated thiophene side chains instead of alkyl substituents on the BDT unit (BDTT) and synthesized the 2D-conjugated copolymer from BDTT and fl uorinated benzotriazole. Nevertheless, the HOMO energy level of this copolymer was relatively high (−5.22 eV), which limited V oc s of the devices to less than 0.8 V and the PCEs recorded were less than 7%.Recently, incorporation of alkylthio side chains on the 4,8-di(thiophen-2-yl)benzo[1,2-b :4,5-b ′]dithiophene (BDTT) unit has been used to effectively down-shift the HOMO energy levels and thereby increase V oc s of the donor polymers. [ 15 ] This is mainly attributed to π-electron accepting capability of divalent sulfur from the p-orbital of the carbon-carbon double bond into its empty 3d-orbitals. [ 16 ] Li and co-workers [ 17 ] reported a BDTTbased low bandgap polymer by introducing branched alkylthio side chains onto the BDTT unit of the well-known photovoltaic polymer, PTB7. This polymer had a low-lying HOMO energy level and highly enhanced hole mobility and photovoltaic properties. Subsequently, Hou and co-workers [ 18 ] also attached linear octylthio side chains on the BDTT unit to improve the short-circuit current ( J sc ) (17.46 mA cm −2 ) of the resulting low bandgap (1.51 eV) polymer PBDT-TS1 while keeping the high V oc (0.8 eV) of the original backbone and achieved a PCE of 9.48%.

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“…Recently, fluorination has attracted much attention due to its multiple effects on the photophysical properties of conjugated polymers, the strong electron‐withdrawing capability of the fluorine atom could effectively adjust the energy levels of polymers with minor influences on their bandgaps and induce the strong dipole along the CF bond, resulting in strong inter/intramolecular interactions, which is favorable for improving charge transport properties . In 2015, a WBG polymer poly(4,8‐bis(5‐(2‐ethylhexyl)thiophen‐2‐yl)benzo[1,2‐ b :4,5‐ b ′]dithiophene) (PBDTT) was synthesized with a high extinction coefficient and a good energy level alignment with PC 71 BM, and the PSCs based on PBDTT:PC 71 BM gave a PCE of 6.12% . In this work, we designed and synthesized a new WBG polymer PBBF (see Figure a) based on fluorinated thienyl (BDTT‐F) units with a fluorine atom and the thienyl‐substituted benzodithiophene (BDTT).…”

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confidence: 99%

High‐Performance Nonfullerene Polymer Solar Cells Based on a Wide‐Bandgap Polymer without Extra Treatment

Chang

et al. 2018

Macromol. Rapid Commun.

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thermal conditions, have impeded the further improvement of the photovoltaic performances of PSCs. [13][14][15][16][17][18][19] Recently, the nonfullerene small molecular electron acceptors such as ITIC, [20] IDIC, [21] and IT-4F [22] have rapidly developed because of their advantages of easy synthesis, strong absorption, easily tunable energy levels, and excellent stability. [23,24] To date, the power conversion efficiencies (PCEs) of nonfullerene PSCs have reached up to ≈14%. [25,26] Nonfullerene electron acceptors, the backbones of which are generally highly planar, possess strong absorption in the range of approx. 500-800 nm, high crystallinity, and high electron mobility in thin film. When it is blended with the wide-bandgap (WBG) polymer, a complementary absorption will be formed to make full use of sunlight and thus enhance the short-circuit current density ( J sc ) of the devices. [27][28][29][30] Therefore, great efforts have been devoted to develop high-performance WBG polymer donors for highly efficient nonfullerene PSCs. [31][32][33][34] Among various polymer donor materials, 2D-conjugated poly mers based on benzodithiophene (BDT) with conjugated side chains exhibit superior photovoltaic performance due to their extended conjugation and enhanced intermolecular π-π interactions. [35][36][37][38] Recently, fluorination has attracted much attention due to its multiple effects on the photophysical properties of conjugated polymers, the strong electron-withdrawing capability of the fluorine atom could effectively adjust the energy levels of polymers with minor influences on their bandgaps and induce the strong dipole along the CF bond, resulting in strong inter/intramolecular interactions, which is favorable for improving charge transport properties. [7,34,[39][40][41][42] In 2015, a WBG polymer poly(4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b′]dithiophene) (PBDTT) was synthesized with a high extinction coefficient and a good energy level alignment with PC 71 BM, and the PSCs based on PBDTT:PC 71 BM gave a PCE of 6.12%. [43] In this work, we designed and synthesized a new WBG polymer PBBF (see Figure 1a) based on fluorinated thienyl (BDTT-F) units with a fluorine atom and the thienyl-substituted benzodithiophene (BDTT). Compared with the nonfluorinated PBDTT, PBBF exhibits slightly red-shifted absorption edge with an optical bandgap (E g opt ) of 2.05 eV and a deeper highest occupied molecular orbital (HOMO) energy level of −5.52 eV (−5.45 eV for PBDTT), which is beneficial Solar Cells Nonfullerene polymer solar cells (PSCs) are developed based on a fluorinated thienyl-based wide-bandgap (WBG) polymer PBBF as the electron donor and nonfullerene small molecule IDIC as the electron acceptor. PBBF exhibits a strong absorption in the range of 300-605 nm with a wide optical bandgap of 2.05 eV, which is complementary with that of IDIC. Meanwhile, it possesses a deeper highest occupied molecular orbital energy level of −5.52 eV and a higher hole mobility of 7.3 × 10 −4 cm 2 V −1 s −1 compared to the ...

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Poly(benzodithiophene) Homopolymer for High-Performance Polymer Solar Cells with Open-Circuit Voltage of Near 1 V: A Superior Candidate To Substitute for Poly(3-hexylthiophene) as Wide Bandgap Polymer

Cited by 41 publications

References 70 publications

Recent Advances in Wide‐Bandgap Photovoltaic Polymers

Recent Advances in Wide‐Bandgap Photovoltaic Polymers

High Bandgap (1.9 eV) Polymer with Over 8% Efficiency in Bulk Heterojunction Solar Cells

High‐Performance Nonfullerene Polymer Solar Cells Based on a Wide‐Bandgap Polymer without Extra Treatment

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