Mode of action of the third component in ternary organic photovoltaic blend PBDB-T/ITIC:PC70BM revealed by EPR spectroscopy

Popov, Alexander; Uvarov, Mikhail N.; Кулик, Л. В.

doi:10.1016/j.synthmet.2021.116783

Cited by 6 publications

(13 citation statements)

References 69 publications

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“…The out-of-phase ESEEM traces for the P3HT/s-SWCNT composite ( Figure 3 ) were also similar to those previously observed in organic donor/acceptor bulk heterojunction composites and can be modeled using the same approach [ 32 ]. The dependence of the out-of-phase ESE intensity M x ( τ ) on the interval τ between two echo-forming microwave pulses is determined by the interspin distance distribution function G ( R ):

where T 2 is the transversal relaxation time for electron spins, R is the distance between the centers of spin density distributions of the electron and the hole, θ and ϕ are the polar and azimuthal angles, respectively, for the vector of the external magnetic field B 0 in the reference frame of the principal axes of zero-field splitting (ZFS) tensor, determined by the dipolar interaction between the spin of the electron and the hole.…”

Section: Resultssupporting

confidence: 74%

“…Since all these ESE traces were accumulated under identical conditions except for different DAF values, a quantitative comparison of the distance distribution density is possible. Again, the distance corresponding to the peak of the distribution density (several nanometers) and its tendency to increase with DAF is similar to those for CTS in other organic photovoltaics donor/acceptor composites [ 30 , 32 ]. However, the decay of G ( R ) with DAF increase for the CTS P3HT + /s-SWCNT − is notably faster than that for CTS in well-known polymer/fullerene composite PCDTBT/PC 70 BM at cryogenic temperatures [ 45 ].…”

Section: Resultssupporting

confidence: 73%

“…For donor–acceptor systems with well-defined geometry, the OOP ESE technique allows the determination of the distance between the positive and the negative charges within the geminate pair (another name of CTS) with angstrom precision [ 28 , 29 ]. Nowadays, it has become a convenient tool for the determination of the structure of CTS in various organic photovoltaic bulk heterojunction composites [ 30 , 31 , 32 ].…”

Section: Introductionmentioning

confidence: 99%

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Fast Recombination of Charge-Transfer State in Organic Photovoltaic Composite of P3HT and Semiconducting Carbon Nanotubes Is the Reason for Its Poor Photovoltaic Performance

Uvarov

Kobeleva

Degtyarenko

et al. 2023

IJMS

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Although the photovoltaic performance of the composite of poly-3-hexylthiophene (P3HT) with semiconducting single-walled carbon nanotubes (s-SWCNT) is promising, the short-circuit current density jSC is much lower than that for typical polymer/fullerene composites. Out-of-phase electron spin echo (ESE) technique with laser excitation of the P3HT/s-SWCNT composite was used to clarify the origin of the poor photogeneration of free charges. The appearance of out-of-phase ESE signal is a solid proof that the charge-transfer state of P3HT+/s-SWCNT− is formed upon photoexcitation and the electron spins of P3HT+ and s-SWCNT− are correlated. No out-of-phase ESE signal was detected in the same experiment with pristine P3HT film. The out-of-phase ESE envelope modulation trace for P3HT/s-SWCNT composite was close to that for the polymer/fullerene photovoltaic composite PCDTBT/PC70BM, which implies a similar distance of initial charge separation in the range 2–4 nm. However, out-of-phase ESE signal decay with delay after laser flash increase for P3HT/s-SWCNT composite was much faster, with a characteristic time of 10 µs at 30 K. This points to the higher geminate recombination rate for the P3HT/s-SWCNT composite, which may be one of the reasons for the relatively poor photovoltaic performance of this system.

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Section: Resultssupporting

confidence: 74%

Section: Resultssupporting

confidence: 73%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Fast Recombination of Charge-Transfer State in Organic Photovoltaic Composite of P3HT and Semiconducting Carbon Nanotubes Is the Reason for Its Poor Photovoltaic Performance

Uvarov

Kobeleva

Degtyarenko

et al. 2023

IJMS

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“…Therefore, the light-induced EPR signal is directly related to the molecular structure of the donor and acceptor and their aggregation behavior, and the degree of structural disorder in the blend film. Continuous wave (CW) light-induced EPR can be used to study the non-geminate (bulk) recombination of the photogenerated charges in organic photovoltaic (OPV) composites [11][12][13]. Time-resolved (TR) EPR can be used to probe the CT state in donor-acceptor composites [14][15][16].…”

Section: Introductionmentioning

confidence: 99%

Structure of the Charge-Transfer State in PM6/Y6 and PM6/Y6:YT Composites Studied by Electron Spin Echo Technique

et al. 2023

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Nowadays, Y-shaped non-fullerene acceptors become increasingly important in organic photovoltaics (OPV). Their use in binary and ternary bulk heterojunction composites continuously pushes up the efficiency of OPV devices. However, the mechanism of OPV performance enhancement by the third component of a ternary composite is rarely understood. In the present work, pulse EPR technique was used to reveal the similarities and the differences of photoinduced charge separation process in binary PM6/Y6 and ternary PM6/Y6:Y-T composites, where PM6 is polymer donor, Y6 and Y-T are different non-fullerene acceptors. Out-of-phase electron spin echo signal was detected for both composites, which is the signature of the charge-transfer state (CT state) formed at the donor/acceptor interface upon exciton splitting. Nearly identical distribution of the distances between the electron and the hole constituting the CT state was obtained for these composites from the analysis of this signal. In both cases the average electron-hole distance was 3.5 nm. It implies that OPV efficiency increase with Y-T addition is not caused by the increased probability of CT state dissociation followed by free charge generation for PM6/Y6:Y-T composite.

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“…For instance, addition of a small molecular guest might lead to the removal of detrimental traps; [ 36 ] likewise, the guest might provide a template for improved structural order of (one of) the host constituents, leading to higher mobility and/or less energetic disorder. [ 37–39 ] While such factors can be included in our model, this is beyond our present purposes and will not be further pursued.…”

Section: Introductionmentioning

confidence: 99%

On the Device Physics of High‐Efficiency Ternary Solar Cells

et al. 2022

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Mixing a third compound into the active layer of an organic bulk heterojunction solar cell to form a ternary system has become an established way to improve performance. Various models, based on different assumptions regarding the active layer morphology and the energetics, have been proposed but there is neither consensus on the applicability of the various assumptions to different experimental systems, nor on the actual device physics of these, mostly qualitative, models. Kinetic Monte Carlo simulations are used to investigate the role of morphology and relative energy levels of the constituent materials. By comparing with experimental current–voltage characteristics, a consistent picture arises when the (minority) third compound is predominantly incorporated between the other (majority) compounds and has energy levels that are intermediate to those of the binary host. Even if morphologically imperfect, the resulting energy cascade promotes charge separation and reduces recombination, leading to higher fill factors and short‐circuit current densities. The open‐circuit voltage sits between that of the binary extremes, in agreement with data from an extensive literature review. This leads to selection criteria for third compounds in terms of energetics and miscibility that promote the formation of a cascade morphology in real and energy space.

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Mode of action of the third component in ternary organic photovoltaic blend PBDB-T/ITIC:PC70BM revealed by EPR spectroscopy

Cited by 6 publications

References 69 publications

Fast Recombination of Charge-Transfer State in Organic Photovoltaic Composite of P3HT and Semiconducting Carbon Nanotubes Is the Reason for Its Poor Photovoltaic Performance

Fast Recombination of Charge-Transfer State in Organic Photovoltaic Composite of P3HT and Semiconducting Carbon Nanotubes Is the Reason for Its Poor Photovoltaic Performance

Structure of the Charge-Transfer State in PM6/Y6 and PM6/Y6:YT Composites Studied by Electron Spin Echo Technique

On the Device Physics of High‐Efficiency Ternary Solar Cells

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