Prolongation of the singlet exciton lifetime of nonfullerene acceptor films by the replacement of the central benzene core with naphthalene

Umeyama, Tomokazu; Igarashi, Kensho; Tamai, Yasukatsu; Wada, Tatsuho; Takeyama, Taiki; Sasada, Daiki; Ishida, Keiichi; Koganezawa, Tomoyuki; Ohtani, Shunsuke; Tanaka, Kazuo; Ohkita, Hideo; Imahori, Hiroshi

doi:10.1039/d0se01861a

Cited by 8 publications

(20 citation statements)

References 65 publications

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“…Therefore, we took the value obtained by the measurement system with a streak camera in this study. Nevertheless, the exciton lifetime of the NTTIC film (180 ps) is longer than that of the ITIC film (140 ps, Figure S9), which is one of the key findings in our previous report …”

Section: Resultssupporting

confidence: 52%

“…As in our previous report regarding NTTIC, NTTIC-F and NTTIC-Cl were synthesized by the Knoevenagel condensation reaction between bis-formylated naphthalene-containing D units and 5,6-dihalogenated 1,1-dicyanomethylene-3-indanone with high yields (>80%). Detailed synthetic procedures are described in the Supporting Information.…”

Section: Resultsmentioning

confidence: 99%

“…Instead, the HOMO energy levels of the NTTIC-F, NTTIC-Cl, and NTTIC films were determined by photoemission yield spectroscopy in air (PYSA, Figure S7b–d). ,− The LUMO energy levels were estimated by adding the optical band gap (Table ) to the HOMO level of the film states. The HOMO/LUMO energy levels of the NTTIC-F, NTTIC-Cl, and NTTIC films were found to be −5.85/–4.23, −5.87/–4.28, and −5.68/–3.96 eV, respectively (Table S1).…”

Section: Resultsmentioning

confidence: 99%

“…To estimate the total efficiency of the ED and CT, the photoluminescence quenching efficiencies of the J71:NFA blend films relative to the neat films were determined (Figure S12). − The wavelengths of 724, 736, and 692 nm were chosen for the preferential excitation of NFAs in the J71:NTTIC-F, J71:NTTIC-Cl, and J71:NTTIC blend films, respectively. When the NFAs were excited, the photoluminescence was efficiently quenched (≥96%) in all the three blend films (Table ).…”

Section: Resultsmentioning

confidence: 99%

“…The design of new A–D–A-type NFA structures, on the basis of well-known ITIC (Figure ) , and Y6 (or BTP-4F, Figure S1), has attracted considerable attention for improving the photovoltaic performance. To investigate the influence of the π-conjugation size of the D core on the film structures, photophysical properties, and photovoltaic performance, we recently prepared a novel A–D–A-type NFA, NTTIC (Figure ), in which the central benzene of ITIC is replaced by naphthalene with a larger π-conjugation size than benzene . The singlet exciton lifetime of the NTTIC film (180 ps) was longer than that of the ITIC film (140 ps) owing to the favorable intermolecular interactions in the NTTIC film.…”

Section: Introductionmentioning

confidence: 99%

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Effect of Terminal-Group Halogenation of Naphthalene-Based Nonfullerene Acceptors on Their Film Structure and Photophysical and Photovoltaic Properties

Umeyama

Wada

Igarashi

et al. 2021

ACS Appl. Energy Mater.

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Terminal-group halogenation is an effective strategy for tuning energy levels, improving light-harvesting ability, and enhancing the intermolecular stacking of nonfullerene acceptors (NFAs) for organic photovoltaic (OPV) devices. Understanding the influence of different halogen atoms on their film structure and photophysical and photovoltaic properties is crucial for designing NFAs. To address this issue, three acceptor−donor−acceptor (A−D− A)-type NFAs, named NTTIC-F, NTTIC-Cl, and NTTIC, were designed. All three NFAs consisted of a naphthalene-containing fusedring as a D core unit and dihalogenated or nonhalogenated 1,1dicyanomethylene-3-indanone groups as terminal A units. NTTIC-Cl exhibited broadened absorption and downshifted energy levels compared to NTTIC-F and NTTIC. Meanwhile, the singlet exciton lifetimes in solution increased in the order of NTTIC < NTTIC-F < NTTIC-Cl, but these were shortened in the pristine films and rather comparable. From grazing-incidence wide-angle X-ray scattering measurements, the tendency of NTTIC-F < NTTIC < NTTIC-Cl was found for the formation of the face-on-oriented packing structures. To the best of our knowledge, this is the first observation of a change in the molecular orientation of NFAs by the type of the halogenation atom at the terminal A unit. When blended with J71 as a conjugated polymer donor, the NTTIC-Cl-based OPV device showed a higher short-circuit current density (J SC , 20.5 mA cm −2 ) than the NTTIC-F-and NTTIC-based devices (19.6 and 15.6 mA cm −2 , respectively). Overall, the power conversion efficiencies of the NTTIC-F-and NTTIC-Cl-based devices were similar (10.6 and 10.5%, respectively) but higher than that of the NTTIC-based device. The former resulted from the higher opencircuit voltage (V OC , 0.812 V) and fill factor (0.666) of the NTTIC-F-based device than those of the NTTIC-Cl-based device (0.793 V and 0.646, respectively).

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Section: Resultssupporting

confidence: 52%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Effect of Terminal-Group Halogenation of Naphthalene-Based Nonfullerene Acceptors on Their Film Structure and Photophysical and Photovoltaic Properties

Umeyama

Wada

Igarashi

et al. 2021

ACS Appl. Energy Mater.

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How to Interpret Transient Absorption Data?: An Overview of Case Studies for Application to Organic Solar Cells

Tamai,

Murata,

Natsuda

et al. 2023

Advanced Energy Materials

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Transient absorption spectroscopy (TAS) is a time‐resolved spectroscopic technique that can quantitatively observe temporal changes in the absorption spectrum associated with transient species, such as excitons and charges. Therefore, it is extensively used in photophysics, photochemistry, and photobiology. TAS plays a crucial role in unveiling charge generation and recombination dynamics in organic solar cells (OSCs). However, the interpretation of TA data is sometimes difficult for those who are not familiar with TAS. In this Perspective, therefore, the utility of TAS is briefly explained in studying OSCs and highlight key considerations for interpreting TA data. Measuring TA data at appropriate excitation fluence and appropriate spectral assignment are essential to correctly interpret photophysics of OSCs. With this Perspective, it aims to offer readers sufficient advice to enable them to perform TA measurements appropriately and interpret the TA data correctly.

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What's Next for Organic Solar Cells? The Frontiers and Challenges

Tamai

2022

Adv Energy and Sustain Res

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The power conversion efficiency (PCE) of organic solar cells (OSCs) is improved dramatically in recent years and now approaches >19% for single‐junction cells and >20% for tandem cells. Therefore, the practical use of OSCs is becoming a reality. This perspective summarizes the state of the art of OSC characteristics and discusses the challenges that remain in further improving PCE. The short‐circuit current density (J SC) of the state‐of‐the‐art OSCs almost approaches 30 mA cm−2. As the internal quantum efficiencies of these devices exceed 90%, for further improvement in J SC, it is necessary to suppress reflection at interfaces and increase the active layer thickness to absorb as many photons as possible. Further suppression of the nonradiative voltage loss is imperative, as there is still large room for improvement compared to inorganic and perovskite counterparts. Hence, increasing the exciton lifetime and photoluminescence quantum yield of nonfullerene acceptors are pivotal to improving the open‐circuit voltage of OSCs. The fill factors of the latest OSCs approach 80%; however, because the optimized active layer thickness remains ≈100 nm, further suppression of bimolecular charge recombination is needed. Finally, this perspective discusses to what extent PCE can be improved and what can be done to achieve this.

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Prolongation of the singlet exciton lifetime of nonfullerene acceptor films by the replacement of the central benzene core with naphthalene

Abstract: The replacement of benzene with naphthalene in the central core of an acceptor achieved a longer singlet lifetime and a higher power conversion efficiency.

Cited by 8 publications

References 65 publications

Effect of Terminal-Group Halogenation of Naphthalene-Based Nonfullerene Acceptors on Their Film Structure and Photophysical and Photovoltaic Properties

Effect of Terminal-Group Halogenation of Naphthalene-Based Nonfullerene Acceptors on Their Film Structure and Photophysical and Photovoltaic Properties

How to Interpret Transient Absorption Data?: An Overview of Case Studies for Application to Organic Solar Cells

What's Next for Organic Solar Cells? The Frontiers and Challenges

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