2,1,3‐Benzothiadiazole‐5,6‐Dicarboxylic Imide – A Versatile Building Block for Additive‐ and Annealing‐Free Processing of Organic Solar Cells with Efficiencies Exceeding 8%

Nielsen, Christian B.; Ashraf, Raja Shahid; Treat, Neil D.; Schroeder, Bob C.; Donaghey, Jenny E.; White, Andrew J. P.; Stingelin, Natalie; McCulloch, Iain

doi:10.1002/adma.201404858

Cited by 87 publications

(84 citation statements)

References 40 publications

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“…[ 19,29 ] The HOMO and LUMO (the lowest unoccupied moleacular orbitals) levels of the two polymers are estimated by cyclic voltammetry (CV) measurements and the optical bandgaps of the polymers (as shown in Table 1 and Figure S1, Supporting Information). The HOMO and LUMO levels are estimated to be ≈−5.33 and −3.62 eV for PffBTT2-DPPT2 and −5.29 and −3.55 eV for PDPPT4, respectively, by cyclic voltammetry.…”

Section: Doi: 101002/aenm201501282mentioning

confidence: 99%

Efficient Low‐Bandgap Polymer Solar Cells with High Open‐Circuit Voltage and Good Stability

Jiang

Chen

et al. 2015

Advanced Energy Materials

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occupied molecular orbital (HOMO) level of the polymer, which has a direct impact on the V OC of the cell. In addition, it is important to achieve low-bandgap PSCs with great stability for the purpose of practical applications. While thermal stability of PSCs is related to thermal properties of the polymer, air stability can be affected by the HOMO level of the polymer. Polymers with deeper HOMO levels are generally more stable against the oxidation by air. Lastly, high-performance low-bandgap polymers should also exhibit high charge transport ability in order to achieve high fi ll factors (FF). [ 24,25 ] Among the reported low bandgap polymers, diketopyrrolopyrrole (DPP) has been a commonly used building block due to its excellent properties such as strong absorption covering near-infrared and visible regions, its electron defi cient nature and high charge carrier mobility. A polymer (DT-PDPP2T-TT) has been reported as the best low-bandgap polymer, which could achieve an impressive short-circuit current density ( J sc) of 20.07 mA cm −2 with diphenolether as additive. The open circuit voltage ( V OC ) of cell is still relatively low (0.67 V) due to the relatively electron-rich nature of thienothiophene-based donor unit. [ 13 ] Another high-performance low-bandgap polymer is C3-DPPTT-T (with a high effi ciency up to 8.8%), which offers an excellent J sc up to 23.5 mA cm −2 but still exhibits a V OC of 0.57 V. [ 17 ] To increase the V OC of DPP-based low bandgap polymers, an effective strategy is to copolymerize the DPP unit with donor building blocks that are less electron-rich than thiophene or thienothiophene. When a benzodithiophene unit was copolymerized with DPP, a signifi cantly higher V OC of 0.73 V was achieved, but the cell effi ciency was signifi cantly lower (6.6% for single junction cell). [ 10 ] Recently, a DPP-based D 1 -A-D 2 -Atype low bandgap polymer (PDPP3T alt TPT) was reported with the introduction of a phenyl ring between two DPP2T moieties. This polymer further increases the V OC to 0.75 V and can achieve an excellent PCE of 8.0%. [ 16 ] In this paper, we report a novel DPP polymer (named poly(difluorobenzothiadiazole-bisthiophene-alt -diketopyrrolopyrrole-bisthiophene) or PffBTT2-DPPT2) that combines a D-A 1 -D-A 2 copolymer strategy and our temperature-dependent aggregation polymer design. The chemical structure of PffBTT2-DPPT2 is shown in Figure 1 a. While the fi rst acceptor unit (A 1 ) is DPP, 5,6-difl uoro-2,1,3-benzothiadiazole (ffBT) is selected as the second acceptor unit (A 2 ), as it was shown in our previous studies to introduce excellent polymer properties for high-effi ciency PSCs. [ 8 ] Although the bandgap of PffBTT2-DPPT2 is small (1.43 eV), PSCs based on PffBTT2-DPPT2 can still achieve an impressive V OC of 0.81 V, indicating a very small V OC loss of 0.62 V. The bandgap and V OC loss of PffBTT2-DPPT2-based PSCs are very close to the optimal Polymer solar cells (PSCs) have been developed as a promising low-cost and environmentally friendly alternative to conventional inorg...

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Section: Doi: 101002/aenm201501282mentioning

confidence: 99%

Efficient Low‐Bandgap Polymer Solar Cells with High Open‐Circuit Voltage and Good Stability

Jiang

Chen

et al. 2015

Advanced Energy Materials

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“…WBG polymers can be synthesized by using moderate electron‐donating and electron‐withdrawing D–A pairs 10, 11, 12, 13, 14, 15, 16. For instance, Sun and co‐workers showed a successful example of poly{dithieno[2,3‐ d :2′,3′‐ d′ ]benzo[1,2‐ b :4,5‐ b′ ]dithiophene‐ co ‐1,3‐bis(thiophen‐2‐yl)‐benzo‐[1,2‐ c :4,5‐ c′ ]dithiophene‐4,8‐dione} (PDBT‐T1), which has a bandgap of 1.85 eV and a high PCE of 9.7%.…”

Section: Introductionmentioning

confidence: 99%

“…[[qv: 10g]] Among the reported building blocks for WBG polymers, benzotriazole (BTA) unit has attracted much interest, since the lone electron pair on the 2‐position nitrogen atom reduces the electron–acceptor ability when compared to the thiadiazole‐based counterparts. [[qv: 10a,c]] It was also noted that the cyclic‐imide fused benzodiathiazole unit has recently been successfully employed as the electron‐accepting unit for the construction of low band‐gap conjugated polymers,11 since the cyclic imide can simultaneously reduce both LUMO and HOMO energy levels of the conjugated polymers. Inspired by the merits of the cyclic‐imide substituent in the conjugated backbone, we designed and synthesized a novel acceptor unit of cyclic‐imide substituted BTA, 4,8‐di(thien‐2‐yl)‐6‐octyl‐2‐octyl‐5 H‐ pyrrolo[3,4‐ f ]benzotriazole‐5,7(6 H )‐dione (TZBI; Scheme 1 ), for producing WBG polymers.…”

Section: Introductionmentioning

confidence: 99%

High‐Performance Polymer Solar Cells Based on a Wide‐Bandgap Polymer Containing Pyrrolo[3,4‐f]benzotriazole‐5,7‐dione with a Power Conversion Efficiency of 8.63%

Lan

Chen

et al. 2016

Advanced Science

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A novel donor–acceptor type conjugated polymer based on a building block of 4,8‐di(thien‐2‐yl)‐6‐octyl‐2‐octyl‐5H‐pyrrolo[3,4‐f]benzotriazole‐5,7(6H)‐dione (TZBI) as the acceptor unit and 4,8‐bis(5‐(2‐ethylhexyl)thiophen‐2‐yl)benzo[1,2‐b:4,5‐b′]dithiophene as the donor unit, named as PTZBIBDT, is developed and used as an electron‐donating material in bulk‐heterojunction polymer solar cells. The resulting copolymer exhibits a wide bandgap of 1.81 eV along with relatively deep highest occupied molecular orbital energy level of −5.34 eV. Based on the optimized processing conditions, including thermal annealing, and the use of a water/alcohol cathode interlayer, the single‐junction polymer solar cell based on PTZBIBDT:PC71BM ([6,6]‐phenyl‐C71‐butyric acid methyl ester) blend film affords a power conversion efficiency of 8.63% with an open‐circuit voltage of 0.87 V, a short circuit current of 13.50 mA cm−2, and a fill factor of 73.95%, which is among the highest values reported for wide‐bandgap polymers‐based single‐junction organic solar cells. The morphology studies on the PTZBIBDT:PC71BM blend film indicate that a fibrillar network can be formed and the extent of phase separation can be manipulated by thermal annealing. These results indicate that the TZBI unit is a very promising building block for the synthesis of wide‐bandgap polymers for high‐performance single‐junction and tandem (or multijunction) organic solar cells.

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“…106 As we discussed in the Section 2.4, the locations of the fullerene molecules over the conjugated polymer backbones depend on the nature and position of the alkyl side-chains. 162 Furthermore, intermolecular interactions between polymer chains and fullerene molecules are known to play crucial roles on the electron-transfer rates, 163 exciton binding energies, 164 and processes of charge separation and charge recombination. 163 Hence, the performance of OPV devices does depend on the intermolecular arrangements and resulting energy landscapes at the interfaces between the polymer and fullerene phases.…”

Section: Noncovalent Interactions In Fullerenes Andmentioning

confidence: 99%

Noncovalent Interactions in Organic Electronic Materials

Ravva

Risko

Brédas

2017

Non-Covalent Interactions in Quantum Chemistry and Physics

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In this Chapter, we provide an overview of how noncovalent interactions, determined by the chemical structure of π-conjugated molecules and polymers, govern essential aspects of the electronic, optical, and mechanical characteristics of organic semiconductors. We begin by describing general aspects of materials design, including the wide variety of chemistries exploited to control the electronic and optical properties of these materials. We then discuss explicit examples of how the study of noncovalent interactions can provide deeper chemical insights that can improve the design of new generations of organic electronic materials.2

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2,1,3‐Benzothiadiazole‐5,6‐Dicarboxylic Imide – A Versatile Building Block for Additive‐ and Annealing‐Free Processing of Organic Solar Cells with Efficiencies Exceeding 8%

Cited by 87 publications

References 40 publications

Efficient Low‐Bandgap Polymer Solar Cells with High Open‐Circuit Voltage and Good Stability

Efficient Low‐Bandgap Polymer Solar Cells with High Open‐Circuit Voltage and Good Stability

High‐Performance Polymer Solar Cells Based on a Wide‐Bandgap Polymer Containing Pyrrolo[3,4‐f]benzotriazole‐5,7‐dione with a Power Conversion Efficiency of 8.63%

Noncovalent Interactions in Organic Electronic Materials

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