<i>cis</i>-1 Isomers of tethered bismethano[70]fullerene as electron acceptors in organic photovoltaics

Umeyama, Tomokazu; Takahara, Shiro; Shibata, Sho; Igarashi, Kensho; Higashino, Tomohiro; Mishima, Kenji; Yamashita, Koichi; Imahori, Hiroshi

doi:10.1039/c8ra02896f

Cited by 9 publications

(6 citation statements)

References 49 publications

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“…In our present work, this effect can be even more pronounced since the synthetic methodologies employed produced amounts of β1-isomer up to 30% [37,40]. It is worth mentioning that the effect of isomers of C 70 -based mono-adducts in OPVs has been receiving special attention [16,[41][42][43][44] by the group of Prof Imahori at Kyoto University and a very recent review by this group [41] calls the attention of the research community to the great importance of this issue which has been so far largely ignored.…”

Section: Resultsmentioning

confidence: 61%

PffBT4T-2OD Based Solar Cells with Aryl-Substituted N-Methyl-Fulleropyrrolidine Acceptors

et al. 2019

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Novel C60 and C70 N-methyl-fulleropyrrolidine derivatives, containing both electron withdrawing and electron donating substituent groups, were synthesized by the well-known Prato reaction. The corresponding highest occupied molecular orbital (HOMO)/lowest unoccupied molecular orbital (LUMO) energy levels were determined by cyclic voltammetry, from the onset oxidation and reduction potentials, respectively. Some of the novel fullerenes have higher LUMO levels than the standards PC61BM and PC71BM. When tested in PffBT4T-2OD based polymer solar cells, with the standard architecture ITO/PEDOT:PSS/Active-Layer/Ca/Al, these fullerenes do not bring about any efficiency improvements compared to the standard PC71BM system, however they show how the electronic nature of the different substituents strongly affects the efficiency of the corresponding organic photovoltaic (OPV) devices. The functionalization of C70 yields a mixture of regioisomers and density functional theory (DFT) calculations show that these have systematically different electronic properties. This electronic inhomogeneity is likely responsible for the lower performance observed in devices containing C70 derivatives. These results help to understand how new fullerene acceptors can affect the performance of OPV devices.

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Section: Resultsmentioning

confidence: 61%

PffBT4T-2OD Based Solar Cells with Aryl-Substituted N-Methyl-Fulleropyrrolidine Acceptors

et al. 2019

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“…Consistently, the quenching efficiency of P3HT fluorescence was higher in P3HT:α-2-α-[70]BIEC (95%) than P3HT: cis -2-[70]BIEC (89%) and P3HT:mono-[70]BIEC (86%), that is, the excitons generated in the P3HT domains reach to the P3HT-fullerene interface efficiently in P3HT:α-2-α-[70]BIEC with the relatively small domain size. Overall, these results proved the utility of [70]fullerene bisadduct cis -isomers, encouraging us to prepare α-1-α isomer of [70]fullerene bisadduct acceptors with the closest proximity of the two added groups on the [70]fullerene cage . Propylene-tethered α-1-α bismethano[70]fullerene with two ethyl groups (α-1-α-[70]PBC; Figure c) was synthesized and isolated.…”

Section: Isomer Separation Of Fullerene Bisadducts For Opvsmentioning

confidence: 86%

“…However, the PCE of a device based on α-1-α-[70]PBC with an amorphous conjugated polymer, PCDTBT (Figure d), was lower (PCE = 3.25%, J SC = 6.35 mA cm –2 , V OC = 0.864 V, FF = 0.593) than that with cis -1-[70]PBC (PCE = 4.60%, J SC = 9.24 mA cm –2 , V OC = 0.844 V, FF = 0.590), i.e., a mixture of α-1-α and α-1-β isomers (Figure c), despite removing the inhomogeneity of the structure and electronic properties of the fullerene bisadducts. In spite of amorphous nature of PCDTBT, the decreased solubility and enhanced aggregation behavior of α-1-α-[70]PBC relative to cis -1-[70]PBC led to the formation of micrometer-sized aggregates in the PCDTBT:α-1-α-[70]PBC blend film and deteriorated the OPV performance, whereas such large aggregates were absent in the PCDTBT: cis -1-[70]PBC film . These results suggest that the optimization of the substituent structure is indispensable for forming bicontinuous structures in the blend films and taking full advantage of regioisomerically pure α-1-α bisadducts of [70]fullerene as electron-accepting materials.…”

Section: Isomer Separation Of Fullerene Bisadducts For Opvsmentioning

confidence: 99%

Isomer Effects of Fullerene Derivatives on Organic Photovoltaics and Perovskite Solar Cells

2019

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Conspectus Solar energy conversion is one of the most important issues for creating and maintaining a future sustainable society. In this regard, photovoltaic technologies have attracted much attention because of their potential to solve energy and environmental issues. In particular, thin-film solar cells, such as organic photovoltaics (OPVs) and perovskite solar cells (PSCs), are highly promising owing to their flexibility, light weight, and low-cost production. One of the most important factors used to evaluate solar-cell performance is the power conversion efficiency (PCE), which is the ratio of the output electric power divided by the input light power. The PCEs of PSCs have become comparable to those of multicrystalline silicon solar cells in a laboratory level, but the PCEs of OPVs have yet to catch up with them and still need to be improved. The insufficient durability of PSCs and OPVs is also a challenge that needs to be addressed. Fullerene derivatives have been utilized as electron acceptors and electron-transport materials in OPVs and PSCs. However, the use of fullerene derivatives requires attention to their isomers if they are multiadducts or even monoadducts produced from fullerenes with low symmetry. Their nonuniform structures and electronic properties may exert a negative effect on photovoltaic properties. However, most researchers in the field of OPVs and PSCs have been unaware of the importance of the isomerism. Even the most prevalent, high-performance fullerene acceptor, [6,6]-phenyl-C71-butyric acid methyl ester ([70]PCBM), has been used as an isomer mixture. In this Account, we summarize recent studies on the effects of isomer separation of fullerene derivatives on the device performances of OPVs and PSCs. Largely, fullerene derivatives containing various isomers are categorized into [60]fullerene bisadducts, [70]fullerene bisadducts, and [70]fullerene monoadducts. In all cases, the difference in isomerism was found to have a large impact on PCEs. The miscibility with polymer donors and film-forming property of fullerene derivatives were affected by the isomer separations, which exert the most potent influence on device performances. Although the disorders in energy levels among isomers are not definitely influencing on photovoltaic properties of isomer mixtures, the molecular packing structures of fullerene derivatives make a significant effect on their photovoltaic properties. Notably, isomerically pure fullerene derivatives oftenbut not alwaysexhibit higher PCEs than the isomer mixture. The search for the best isomers of fullerene derivatives and their optimal compositional ratios, which extensively depend on their roles and the combined materials, will be an indispensable step to achieving consistently higher device performances for OPVs and PSCs.

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“…3) A too bulky side group is detrimental to the compact packing of fullerenes, which will distinctly decrease the electron mobility of fullerene films (Figure 3b), and result in lower J sc and FF values (Figure S38, Supporting Information). [23,29] In order to obtain a higher PCE for planar structure PSCs, two main issues, photon absorption/conversion and current leakage, need to be considered according to the revised detailed balance model. [30] The former mostly depends on the type and quality of perovskite absorber, while the latter is related to the electron transport process including charge transport layers and heterojunction interfaces of perovskite/ETLs.…”

Section: The Structure-dependent Effects Of Fullerene Derivatives On Photovoltaics Parametersmentioning

confidence: 99%

Multifunctional Molecular Design of a New Fulleropyrrolidine Electron Transport Material Family Engenders High Performance of Perovskite Solar Cells

Zhou

et al. 2021

Adv Funct Materials

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C 61 -butyric acid methyl ester remains indispensable as the electron transport material (ETM) for perovskite solar cells (PSCs), but its synthesis involves complicated multisteps with low productivity. In contrast, the potential of synthesizing simpler fulleropyrrolidine derivatives has long been overlooked, and little has been understood regarding their structuredependent effects on photovoltaic (PV) performance. Herein, seven novel fulleropyrrolidine derivatives (F1-F7) are deliberately designed, synthesized, and comprehensively characterized in both solution and thin-film states and subsequently investigated as ETMs for PSCs. Notably, the F4 delivers the highest power conversion efficiencies over 20% of devices, which surpass all reported fulleropyrrolidine ETMs due to its optimal photoelectric property. Moreover, the structure-dependent effects of the fullerenes on PV parameters are uncovered, including solubility, intermolecular interaction, packing structure, and charge-transfer ability, which can guide the future design of highperformance and stable fullerene ETMs for PSCs.

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cis-1 Isomers of tethered bismethano[70]fullerene as electron acceptors in organic photovoltaics

Cited by 9 publications

References 49 publications

PffBT4T-2OD Based Solar Cells with Aryl-Substituted N-Methyl-Fulleropyrrolidine Acceptors

PffBT4T-2OD Based Solar Cells with Aryl-Substituted N-Methyl-Fulleropyrrolidine Acceptors

Isomer Effects of Fullerene Derivatives on Organic Photovoltaics and Perovskite Solar Cells

Multifunctional Molecular Design of a New Fulleropyrrolidine Electron Transport Material Family Engenders High Performance of Perovskite Solar Cells

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