End‐Capping Effect of a Narrow Bandgap Conjugated Polymer on Bulk Heterojunction Solar Cells

Park, Jin Kuen; Jo, Jang; Seo, Jung Hwa; Moon, Ji Sun; Park, Yeong Don; Lee, Kwanghee; Heeger, Alan J.; Bazan, Guillermo C.

doi:10.1002/adma.201004629

Cited by 176 publications

(151 citation statements)

References 28 publications

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“…2TPD has been prepared via a sixstep synthesis route, starting from a Gewald-type condensation between methyl pyruvate, ethyl 2-cyanoacetate, and sulfur to obtain the heterocyclic core structure, [40,41] as described in the Experimental Section and Figure S2 (Supporting Information). The polymers were end-capped and purified to remove any Pd or Sn residues, [42][43][44] as described in detail in the Supporting Information. We used 2-octyldodecyl side chains on 2TPD to increase the solubility of the resulting polymer and also provide satisfactory steric hindrance to prevent aggregation.…”

Section: Doi: 101002/adma201706584mentioning

confidence: 99%

Efficient Near‐Infrared Electroluminescence at 840 nm with “Metal‐Free” Small‐Molecule:Polymer Blends

et al. 2018

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The development of efficient and biocompatible organic near-infrared emitters is attractive for many applications, spanning from photodynamic therapy [1] to light fidelity (Li-Fi) all-optical networking systems. [2][3][4] In particular, the range 700-1000 nm is interesting for medical applications, given the semitransparency of biological tissue in this spectral interval, [5] and we will specifically refer to this range as near-infrared (NIR) in the following text. Compared to conventional inorganic materials, organic NIR emitters are interesting also for their mechanical conformability, which makes them appealing for the integration in flexible and stretchable devices. [6] Furthermore, the metal-free organic light-emitting materials can be a cheap and biocompatible alternative to inorganic ones for application in wearable, implantable, or in vivo medical applications, such as for sensing of body temperature, heart and respiration rates, blood pressure, glucose level, and oxygenation. [7] In the search for ever-higher efficiencies, several classes of materials have been investigated, such as perovskite-structured methylammonium lead halides, [8][9][10] quantum dots, [11] and organometallic phosphorescent complexes. [12][13][14][15][16][17][18][19] However, although such hybrid materials afford substantial electroluminescence (EL) external quantum efficiency (EQE) in the NIR, in some cases exceeding 10% [8,10] or even 20% or so, [13] their use of heavy, toxic, and/or costly metals is not ideal for manufacturing, sustainability, environmental impact, and, in perspective, biocompatibility. Furthermore, in such hybrid systems, and in general in materials that leverage triplet excitons to boost the EQE, [20,21] exciton recombination dynamics typically fall in the hundreds of nanoseconds or even in the microsecond (or longer) range, which intrinsically limits the bandwidth when integrated in devices for telecommunications. For Li-Fi applications, [2][3][4] fluorescent molecular and polymeric materials are preferred, given that the typical fluorescence lifetime of these materials is of the order of few nanoseconds or less, thereby ideally allowing data transmission rates up to the Gb s −1 regime.In the last decade, scientists have attempted different strategies to develop heavy-metal-free NIR fluorescent organic light-emitting diodes (OLEDs), with chemical design essentially revolving around the careful combination of donor and acceptor groups to both tune the spectral range (up to 1000 nm) and maximize the EQE. [22][23][24][25][26][27][28][29][30][31][32][33] Very recently, we have, for Due to the so-called energy-gap law and aggregation quenching, the efficiency of organic light-emitting diodes (OLEDs) emitting above 800 nm is significantly lower than that of visible ones. Successful exploitation of triplet emission in phosphorescent materials containing heavy metals has been reported, with OLEDs achieving remarkable external quantum efficiencies (EQEs) up to 3.8% (peak wavelength > 800 nm). For OLEDs incorporating f...

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Section: Doi: 101002/adma201706584mentioning

confidence: 99%

Efficient Near‐Infrared Electroluminescence at 840 nm with “Metal‐Free” Small‐Molecule:Polymer Blends

et al. 2018

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“…This prevents reactive end groups from acting as charge trapping sites in electronic devices. [ 24 ] The polymers were purifi ed by precipitation in methanol followed by Soxhlet extraction with acetone and hexane to remove residual catalyst and low molecular weight oligomers. The polymers were then dissolved in chloroform and precipitated again into methanol.…”

Section: Polymer Synthesis and Characterizationmentioning

confidence: 99%

Highly Efficient Inverted Organic Solar Cells Through Material and Interfacial Engineering of Indacenodithieno[3,2‐b]thiophene‐Based Polymers and Devices

Intemann

Yao

et al. 2013

Adv Funct Materials

134

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A synergistic approach combining new material design and interfacial engineering of devices is adopted to produce high efficiency inverted solar cells. Two new polymers, based on an indacenodithieno[3,2‐b]thiophene‐difluorobenzothiadiazole (PIDTT‐DFBT) donor–acceptor (D–A) polymer, are produced by incorporating either an alkyl thiophene (PIDTT‐DFBT‐T) or alkyl thieno[3,2‐b]thiophene (PIDTT‐DFBT‐TT) π‐bridge as spacer. Although the PIDTT‐DFBT‐TT polymer exhibits decreased absorption at longer wavelengths and increased absorption at higher energy wavelengths, it shows higher power conversion efficiencies in devices. In contrast, the thiophene bridged PIDTT‐DFBT‐T shows a similar change in its absorption spectrum, but its low molecular weight leads to reduced hole mobilities and performance in photovoltaic cells. Inverted solar cells based on PIDTT‐DFBT‐TT are explored by modifying the electron‐transporting ZnO layer with a fullerene self‐assembled monolayer and the MoO3 hole‐transporting layer with graphene oxide. This leads to power conversion efficiencies as high as 7.3% in inverted cells. PIDTT‐DFBT‐TT's characteristic strong short wavelength absorption and high efficiency suggests it is a good candidate as a wide band gap material for tandem solar cells.

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“…The purity [101][102][103] and the end group effect [104][105][106] on the performance of transistor materials and OPV materials have also been investigated. However, as the exact determination of "contaminant" or "purity level" of a given material, especially for polymers, is very difficult to achieve, the attempts to correlate the performance of an "impure" material to the existence of some extrinsic impurity would be questionable.…”

Section: Molecular Weight and Purity Of The Polymermentioning

confidence: 99%

“…However, as the exact determination of "contaminant" or "purity level" of a given material, especially for polymers, is very difficult to achieve, the attempts to correlate the performance of an "impure" material to the existence of some extrinsic impurity would be questionable. Even though the end capping strategy has been found efficient to improve the performance of the polymer [104][105][106], it is still not commonly adopted by research groups, even not routinely used by the groups who claimed the positive effect. Questions such as how the end group influences the performance of the polymer, what kinds of impurities are detrimental to the performance and what kinds of impurities serve as friendly dopants still remain unaddressed.…”

Section: Molecular Weight and Purity Of The Polymermentioning

confidence: 99%

Bulk Heterojunction Solar Cells — Opportunities and Challenges

Ye¹,

Xu²

2015

Solar Cells - New Approaches and Reviews

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End‐Capping Effect of a Narrow Bandgap Conjugated Polymer on Bulk Heterojunction Solar Cells

Cited by 176 publications

References 28 publications

Efficient Near‐Infrared Electroluminescence at 840 nm with “Metal‐Free” Small‐Molecule:Polymer Blends

Efficient Near‐Infrared Electroluminescence at 840 nm with “Metal‐Free” Small‐Molecule:Polymer Blends

Highly Efficient Inverted Organic Solar Cells Through Material and Interfacial Engineering of Indacenodithieno[3,2‐b]thiophene‐Based Polymers and Devices

Bulk Heterojunction Solar Cells — Opportunities and Challenges

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