Designing Nonfullerene Acceptors with Oligo(Ethylene Glycol) Side Chains: Unraveling the Origin of Increased Open‐Circuit Voltage and Balanced Charge Carrier Mobilities

Cui, Junjie; Park, Jung-Hwa; Kim, Dong Won; Choi, Minwoo; Chung, Hae Yeon; Kwon, Oh Nam; Kwon, Ji Eon; Park, Soo Young

doi:10.1002/asia.202100660

Cited by 4 publications

(6 citation statements)

References 32 publications

(35 reference statements)

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“…This difference in chemical structures induces differences in exciton characteristics and the charge separation mechanism in organic photovoltaic devices ( vide infra ). As an acceptor, a highly crystalline dicyanodistyrylbenzene-based nonfullerene acceptor NIDCSEO3 with OEG side chains on the NIDCS backbone was employed, whose solubility in various aromatic solvents is excellent to give high-quality PSC devices. ,, Importantly, the π–π stacking of the acceptor material and thus the crystallinity of the resulting film is highly enhanced due to the flexible OEG chains, providing an ideal D/A blend morphology in the photoactive layer.…”

Section: Resultsmentioning

confidence: 99%

“…(a) Photocurrent density–effective voltage ( J ph – V eff ) characteristics and (b) current density–voltage ( J – V ) curves for PTB7:NIDCSEO3 and P3HT:NIDCSEO3 PSCs (Error bars represent the standard deviation from the mean). Reprinted with permission from ref . Copyright (2021) John Wiley & Sons, Inc.…”

Section: Resultsmentioning

confidence: 99%

“…Thus, the formation of a polaron pair is subsequent to the hot exciton formation in P3HT. Both PTB7:NIDCSEO3 and P3HT:NIDCSEO3 blends exhibited strong π–π stacking in both D and A regions with a highly crystalline acceptor, (2 E ,2′ E )-3,3′-(2,5-bis(2-(2-(2-methoxyethoxy)ethoxy)ethoxy)-1,4-phenylene)bis(2-(5-(2-(2-ethylhexyl)-1,3-dioxo-2,3-dihydro-1 H -benzo[de]isoquinolin-6-yl)thiophen-2-yl)acrylonitrile) (NIDCSEO3), with oligo(ethylene glycol) (OEG) side chains, which is favorable for the exciton delocalization within D and A regions and the subsequent charge separation at the D/A interface. − Thus, we could induce the ideal π–π stacked blend morphology and rule out the morphological effect when comparing the charge separation in PTB7:NIDCSEO3 and P3HT:NIDCSEO3 systems and focus our interest on the intrinsic characteristics of the polymer exciton and the relevant charge separation mechanism at the D/A interface. Through the temperature- and pump-dependent transient absorption measurements, different charge separation mechanisms in PTB7:NIDCSEO3 and P3HT:NIDCSEO3 were thoroughly investigated.…”

Section: Introductionmentioning

confidence: 99%

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Influence of Intramolecular Charge-Transfer Characteristics of Excitons on Polaron Generation at the Donor/Acceptor Interface in Polymer Solar Cells

et al. 2021

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To understand the importance of excess energy in the charge separation mechanism in polymer solar cells (PSCs), we focused on the dissociation of the Coulombically bound electron and hole pair at the donor (D) and acceptor (A) interface. A push−pull-type copolymer poly(3-fluorothienothiophenebenzodithiophene) (PTB7) and a homopolymer poly(3-hexylthiophene) (P3HT) were used as model compounds to correlate the chemical structure of the donor materials with the mechanism of photoinduced charge separation at the D/A interface in PSCs. In the case of PTB7, excitons with intramolecular charge-transfer (ICT) characteristics are initially generated due to the push−pull actions between the electron-donating and electron-accepting building units, resulting in electron density displacement to facilitate interfacial charge separation. On the other hand, the delocalized exciton state of P3HT is known to be favorable for the hot exciton dissociation and charge generation while lacking the ICT characteristics. Therefore, understanding the effect of ICT characteristics and delocalization of the exciton state of polymers is important for enhancing the charge separation at the D/A interface and thus the photocurrent in PSCs. Both PTB7:NIDCSEO3 and P3HT:NIDCSEO3 blends exhibited strongly π−π stacked D and A regions with highly crystalline dicyanodistyrylbenzenenaphthalimide-based acceptor, NIDCSEO3, which is beneficial for the exciton delocalization and reduces the effect of blend morphology when comparing the charge separation at the D/A interface. Through the temperature-and pump-dependent femtosecond transient absorption experiments in this work, it was found that the charge separation via the hot CT state is dominant in PTB7:NIDCSEO3 owing to the delocalized ICT-type excitons of PTB7. On the other hand, P3HT:NIDCSEO3 exhibited a complex charge generation mechanism comprising both hot and relaxed states including a polaron pair state within P3HT while preserving the delocalized exciton state based on the highly crystalline homopolymer structure.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Influence of Intramolecular Charge-Transfer Characteristics of Excitons on Polaron Generation at the Donor/Acceptor Interface in Polymer Solar Cells

et al. 2021

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“…Thus, D18:BS3TSe‐4F‐based OSCs achieved a higher PCE of 18.48%. Introducing highly polarizable substituent groups onto semiconductor molecules to improve the dielectric constant is another strategy to reduce E b 127,130,131 . Li et al 127 developed Y6‐4O (Figure 3) via attaching a highly polarizable oligo‐(ethylene glycol) side chain onto the pyrrole unit of Y6 and increased the dielectric constants from 3.36 to 5.13, thus reducing the E b from 0.30 eV (Y6) to 0.24 eV (Y6‐4O) (Figure 8I).…”

Section: Exciton Dissociation In Oscs and Qdscsmentioning

confidence: 99%

Exciton diffusion and dissociation in organic and quantum‐dot solar cells

Zhang

et al. 2023

SmartMat

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For the process of photovoltaic conversion in organic solar cells (OSCs) and quantum‐dot solar cells (QDSCs), three of four steps are determined by exciton behavior, namely, exciton generation, exciton diffusion, and exciton dissociation. Therefore, it is of great importance to regulate exciton behavior in OSCs and QDSCs for achieving high power conversion efficiency. Due to the rapid development in materials and device fabrication, great progress has been made to manage the exciton behavior to achieve prolonged exciton diffusion length and improved exciton dissociation in recent years. In this review, we first introduce the parameters that affect exciton behavior, followed by the methods to measure exciton diffusion length. Then, we provide an overview of the recent advances with regard to exciton behavior investigation in OSCs and QDSCs, including exciton lifetime, exciton diffusion coefficient, and exciton dissociation. Finally, we propose future directions in deepening the understanding of exciton behavior and boosting the performance of OSCs and QDSCs.

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“…A strategy that has been consistently successful and has become the preeminent way to obtain high static dielectric constant organic electronics is the use of ethylene glycol (EG) side chains . These side chains have been added to fullerene derivatives, − ,− , small molecules, − ,, and polymers − ,− and have in turn resulted in increased static dielectric constants. Notably, recent work from Rousseva et al reached a record static dielectric constant for fullerene derivatives (ϵ r > 10) with the BPEG-2 molecule (see Figure ).…”

Section: Introductionmentioning

confidence: 99%

Strategies for Enhancing the Dielectric Constant of Organic Materials

et al. 2022

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High dielectric constant organic semiconductors, often obtained by the use of ethylene glycol (EG) side chains, have gained attention in recent years in the efforts of improving the device performance for various applications. Dielectric constant enhancements due to EGs have been demonstrated extensively, but various effects, such as the choice of the particular molecule and the frequency and temperature regime, that determine the extent of this enhancement require further understanding. In this work, we study these effects by means of polarizable molecular dynamics simulations on a carefully selected set of fullerene derivatives with EG side chains. The selection allows studying the dielectric response in terms of both the number and length of EG chains and also the choice of the group connecting the fullerene to the EG chain. The computed time- and frequency-dependent dielectric responses reveal that the experimentally observed rise of the dielectric constant within the kilo/megahertz regime for some molecules is likely due to the highly stretched dielectric response of the EGs: the initial sharp increase over the first few nanoseconds is followed by a smaller but persistent increase in the range of microseconds. Additionally, our computational protocol allows the separation of different factors that contribute to the overall dielectric constant, providing insights to make several molecular design guides for future organic materials in order to enhance their dielectric constant further.

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Designing Nonfullerene Acceptors with Oligo(Ethylene Glycol) Side Chains: Unraveling the Origin of Increased Open‐Circuit Voltage and Balanced Charge Carrier Mobilities

Cited by 4 publications

References 32 publications

Influence of Intramolecular Charge-Transfer Characteristics of Excitons on Polaron Generation at the Donor/Acceptor Interface in Polymer Solar Cells

Influence of Intramolecular Charge-Transfer Characteristics of Excitons on Polaron Generation at the Donor/Acceptor Interface in Polymer Solar Cells

Exciton diffusion and dissociation in organic and quantum‐dot solar cells

Strategies for Enhancing the Dielectric Constant of Organic Materials

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