Increased open circuit voltage in fluorinated benzothiadiazole-based alternating conjugated polymers

Zhang, Yong; Chien, Shang Chieh; Chen, Kung Shih; Yip, Hin‐Lap; Sun, Ying; Davies, Joshua A.; Chen, Fang‐Chung; Jen, Alex K.‐Y.

doi:10.1039/c1cc14586j

Cited by 244 publications

(212 citation statements)

References 21 publications

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“…Indeed, conventional polycondensation methods do not allow regioselectivity control when using asymmetric monomers [17]. Therefore, the lack of control of the monomer orientation along the conjugated backbone leads to regiorandom polymers [40][41][42][43][44] that are known to suffer from lower structural organization in solid state and consequently possess, most often, inferior charge transport properties [45]. An alternative stepwise chemical approach consists in synthesizing symmetric monomers from unsymmetrical fragments, thanks to their regiochemistry.…”

Section: Methodsmentioning

confidence: 99%

Impact of Backbone Fluorination on π-Conjugated Polymers in Organic Photovoltaic Devices: A Review

et al. 2016

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Solution-processed bulk heterojunction solar cells have experienced a remarkable acceleration in performances in the last two decades, reaching power conversion efficiencies above 10%. This impressive progress is the outcome of a simultaneous development of more advanced device architectures and of optimized semiconducting polymers. Several chemical approaches have been developed to fine-tune the optoelectronics and structural polymer parameters required to reach high efficiencies. Fluorination of the conjugated polymer backbone has appeared recently to be an especially promising approach for the development of efficient semiconducting polymers. As a matter of fact, most currently best-performing semiconducting polymers are using fluorine atoms in their conjugated backbone. In this review, we attempt to give an up-to-date overview of the latest results achieved on fluorinated polymers for solar cells and to highlight general polymer properties' evolution trends related to the fluorination of their conjugated backbone.

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Section: Methodsmentioning

confidence: 99%

Impact of Backbone Fluorination on π-Conjugated Polymers in Organic Photovoltaic Devices: A Review

et al. 2016

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“…Importantly, we found that the l of K 8 Al 8 Si 38 is much superior to those of, e.g., a-Si: 1 cm 2 V À1 s À1 for electrons and 0.01 cm 2 V À1 s À1 for holes [41][42][43][44] and to those of organic materials: $0.008 cm 2 V À1 s À1 for electrons and $0.002 for holes. 45 In addition, the ratio l e =l h is $5 in K 8 Al 8 Si 38 , while it can be as high as 100 in a-Si (it is $3 in c-Si).…”

Section: A Clathratesmentioning

confidence: 99%

Novel silicon phases and nanostructures for solar energy conversion

Wippermann

Vörös

et al. 2016

Applied Physics Reviews

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Silicon exhibits a large variety of different bulk phases, allotropes, and composite structures, such as, e.g., clathrates or nanostructures, at both higher and lower densities compared with diamond-like Si-I. New Si structures continue to be discovered. These novel forms of Si offer exciting prospects to create Si based materials, which are non-toxic and earth-abundant, with properties tailored precisely towards specific applications. We illustrate how such novel Si based materials either in the bulk or as nanostructures may be used to significantly improve the efficiency of solar energy conversion devices.

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“…A comprehensive survey of the chemical methods for designing high PCE polymers found that the inductive effect such as introducing fluorine or sulfur atoms to the polymer backbone has been considered as one of the most effective and successful methods, which can bring about simultaneous improvement of V oc , J sc , and FF on their OSCs devices. 26−30 However, chemically introducing fluorine 31 or sulfur 32 always makes the synthetic route more complicated and expensive, and fluorine atoms sometimes reduce the solubility of the polymers remarkably. shown in Scheme 1, analogous hexyl and cyclohexyl were chosen as side chains because they have the same carbon number and similar electronic effect except they were connected to the polymer backbone with a primary carbon and a secondary carbon, respectively.…”

Section: −5mentioning

confidence: 99%

Intra- and Intermolecular Steric Hindrance Effects Induced Higher Open-Circuit Voltage and Power Conversion Efficiency

Han

Chen

et al. 2015

ACS Macro Lett.

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A pair of donor−acceptor polymers PBDThDTBT and PBDTchDTBT are synthesized, which share the same conjugated backbone, but are designed with hexyl and cyclohexyl side chains, respectively. The stronger steric hindrance of cyclohexyl endows PBDTchDTBT a deeper lying HOMO energy level of −5.39 eV compared to −5.22 eV for PBDThDTBT. However, PBDThDTBT and PBDTchDTBT exhibit a similar optical bandgap around 1.72 eV and a hole mobility around 10 −5 cm 2 V −1 s −1 . Interestingly, the PBDTchDTBT/PC 71 BM blends exhibited higher hole mobility than PBDThDTBT/PC 71 BM after DIO was added. The higher hole mobility and fibrillar network in the active layer endows PBDTchDTBT higher power conversion efficiency of 7.9%, together with simultaneously improved open-circuit voltage of 0.80 V, short-circuit current density of 13.50 mA cm, and fill factor of 72.74% after a systemic study of their solar cell devices. S emiconducting polymer is considered as the ideal material for next generation large area optoelectronics application in virtue of its superior solution processing and film forming ability.1−5 When a semiconducting polymer is employed, research is mainly focused on its frontier molecular orbital energy levels and optical and optoelectronic characteristics, which have reliance on the polymer's planarity, interchain aggregation, alkyl substituents, and molecular weight.6−9 One simple and effective strategy employed to adjust the energy levels and optical property of a semiconducting polymer is intra-or intermolecular steric hindrance effect (SHE). 10−13However, SHE has been reported with negative effect on molecular self-organization in the donor−acceptor (D−A) oligmers.14 Intermolecular SHE introduced to the polymer backbone could prevent molecular packing and then result in weaker crystallinity.15 Intramolecular SHE may reduce the π-orbital overlap between two adjacent units and lead to undesirable hypochromatic shifted absorption spectra and wide bandgap (E g ), 10,16−20 however, as is well-known, wide absorption spectra, and narrow E g of the absorber are crucial for organic solar cells (OSCs) application. 21Although SHE has been considered as a negative effect for polymer's self-aggregation and effective conjugation, one advantage should be pointed out, that is, SHE can significantly decrease the highest occupied molecular orbital (HOMO) energy levels of the polymer. For example, poly(3-cyclohexylthiophene) (P3chT) exhibited more twisted conjugating backbone than poly(3-hexylthiophene) (P3hT) because of stronger SHE of cyclohexyl than hexyl, which resulted in a larger dihedral angle (θ) between the two adjacent thiophene rings together with a wider E g and a deeper lying HOMO of −5.72 eV, 0.72 eV lower than that of P3hT (−5.0 eV) experimentally.10 Theoretically, Bredas and co-workers reported that the ionic potential of the polythiophene increased gradually as the torsion angle increased from 0 to 90°.22 This

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Increased open circuit voltage in fluorinated benzothiadiazole-based alternating conjugated polymers

Abstract: Small band-gap conjugated polymers based on monofluoro- and difluoro-substituted benzothiadiazole were developed. Highly efficient polymer solar cells (PCE as high as 5.40%) could be achieved for devices made from these polymers.

Cited by 244 publications

References 21 publications

Impact of Backbone Fluorination on π-Conjugated Polymers in Organic Photovoltaic Devices: A Review

Impact of Backbone Fluorination on π-Conjugated Polymers in Organic Photovoltaic Devices: A Review

Novel silicon phases and nanostructures for solar energy conversion

Intra- and Intermolecular Steric Hindrance Effects Induced Higher Open-Circuit Voltage and Power Conversion Efficiency

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