Spin-dependent recombination of the charge-transfer state in photovoltaic polymer/fullerene blends

Lukina, Ekaterina A.; Reijerse, Eduard J.; Lubitz, Wolfgang; Кулик, Л. В.

doi:10.1080/00268976.2018.1548713

Cited by 9 publications

(4 citation statements)

References 36 publications

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“…One way to control the CS and CR dynamics is to modulate the energy level of the radical pair (RP) states by changing the solvent polarity or via application of an external electric field; these modifications affect both the singlet and triplet RP states [14, 15] . An alternative approach involves applying an external magnetic field, which serves to lift the degeneracy of the three triplet states (T + , T 0 , and T − ) through Zeeman splitting [16–22] . Magnetic field driven RP mechanisms are generally governed by two effects: 1) hyperfine coupling (HFC), which facilitates the spin conversion (S, T 0 → T − , T + ) and 2) the Δg mechanism that enhances the (S → T 0 ) spin conversion.…”

Section: Figurementioning

confidence: 99%

“…[14,15] An alternative approach involves applying an external magnetic field, which serves to lift the degeneracy of the three triplet states (T + , T 0 , and T À ) through Zeeman splitting. [16][17][18][19][20][21][22] Magnetic field driven RP mechanisms are generally governed by two effects: 1) hyperfine coupling (HFC), which facilitates the spin conversion (S, T 0 ! T À , T + ) and 2) the Dg mechanism that enhances the (S !…”

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confidence: 99%

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Magnetic‐Field‐Induced Modulation of Charge‐Recombination Dynamics in a Rosarin‐Fullerene Complex

Kim

et al. 2021

Angew Chem Int Ed

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Charge‐recombination processes are critical for photovoltaic applications and should be suppressed for efficient charge transport. Here, we report that an applied magnetic field (0–1 T) can be used control the charge‐recombination dynamics in an expanded rosarin‐C60 complex. In the low magnetic field regime (<100 mT), the charge‐recombination rate slows down due to hyperfine coupling, as inferred from transient absorption spectroscopic analyses. In contrast, in the high field regime, i.e., over 500 mT, the charge‐recombination rate recovers and increases because the Δg mechanism facilitates spin conversion to a triplet charge‐separated state (S to T0) that undergoes rapid charge‐recombination to a localized rosarin triplet state. Therefore, we highlight the charge‐recombination rate and the localized triplet state population can be modulated by the magnetic field in charge donor/acceptor non‐covalent complexes.

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Section: Figurementioning

confidence: 99%

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confidence: 99%

Magnetic‐Field‐Induced Modulation of Charge‐Recombination Dynamics in a Rosarin‐Fullerene Complex

Kim

et al. 2021

Angew Chem Int Ed

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“…This correlation arises because the CTS precursor (the exciton formed upon light absorption by the donor or acceptor part of the composite) has a definite electron spin, usually zero (the singlet exciton). The triplet excitons can also contribute to the charge photogeneration in special cases [ 14 ]. An attractive feature of OOP ESE is that it is free from the contribution of any transient species other than CTS.…”

Section: Introductionmentioning

confidence: 99%

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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“…Since this process is fast, the correlation between the electron spins of the electron and the hole constituting the CT state is preserved. It is important that the exciton, as the precursor of the CT state (has a definite electron spin, usually zero (singlet exciton) [22,23], although triplet excitons (spin S = 1) can contribute to charge photogeneration in special cases [24]. The principal reason for the appearance of the OOP ESE is the mutual correlation of the spins of the electron and the hole within the CT state.…”

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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Spin-dependent recombination of the charge-transfer state in photovoltaic polymer/fullerene blends

Cited by 9 publications

References 36 publications

Magnetic‐Field‐Induced Modulation of Charge‐Recombination Dynamics in a Rosarin‐Fullerene Complex

Magnetic‐Field‐Induced Modulation of Charge‐Recombination Dynamics in a Rosarin‐Fullerene Complex

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

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