Remarkable Dependence of the Final Charge Separation Efficiency on the Donor–Acceptor Interaction in Photoinduced Electron Transfer

Higashino, Tomohiro; Yamada, Tomoki; Yamamoto, Masanori; Furube, Akihiro; Tkachenko, Nikolai V.; Miura, Taku; Kobori, Yasuhiro; Jono, Ryota; Yamashita, Koichi; Imahori, Hiroshi

doi:10.1002/ange.201509067

Cited by 27 publications

(8 citation statements)

References 28 publications

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“…The intramolecular CS and CR are the two vital interfacial processes of organic solar cells, whereas the competition with other radiative and non-radiative decay channels directly influences the power conversion efficiency (PCE). For the effectiveness of CS state, CS has to be activationless (−Δ G ≃ λ) and hole–electron recombination should be in the inverted region (−Δ G > λ). , Predicting and tuning the rate constant of these two fundamental processes (rate constants of CS and CR, k CS and k CR , respectively) is the initial step to achieve charge generation efficiency at the interface and model the design of new materials. k CS / k CR is a paramount index for efficiently converting harvested light energy into a CS state .…”

Section: Thermodynamics Of Symmetry-breaking Charge-separationmentioning

confidence: 99%

Symmetry-Breaking Charge Separation in Molecular Constructs for Efficient Light Energy Conversion

Sebastian

Hariharan

2022

ACS Energy Lett.

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The generation of electron–hole radical pair at the active layer of organic photovoltaics through symmetry-breaking charge separation (SB-CS) has a crucial role in enhancing open-circuit voltage (V oc) and thereby increasing power conversion efficiency. Since the SB-CS materials achieve intramolecular charge separation with a negligible energetic driving force and decelerated charge recombination (CR) rate, SB-CS has been subjected to extensive experimental and theoretical studies. This Focus Review assesses the fundamentals of photosynthetic reaction centers, especially the “special pair”, and discusses how covalent control over the geometric arrangement, surrounding dielectric medium, and substitutions on multichromophoric perylenediimide architecture affects the energy landscape of SB-CS and CR. We systematically summarize the kinetically favored undesirable radiative and non-radiative deactivation channels of SB-CS and CR processes on diverse chromophoric arrangements. Here, we suggest new rational design principles to fine-tune the electron-transfer dynamics at the molecular level to improve the performance of light–energy conversion devices.

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Section: Thermodynamics Of Symmetry-breaking Charge-separationmentioning

confidence: 99%

Symmetry-Breaking Charge Separation in Molecular Constructs for Efficient Light Energy Conversion

Sebastian

Hariharan

2022

ACS Energy Lett.

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“…The third reason may be related to the formation of a triplet charge separated state 3 ( -Ir/NiO + ), that might arise from the proximity of the heavy nucleus iridium. Studies investigating the effect of the spin multiplicity of the charge separated state are scarce, however, there are reports by Wasielewski [35][36][37] and other groups [38][39][40][41][42][43] that demonstrate that triplet charge separated states exhibit much longer lifetime than singlet ones, simply because the recombination to the singlet ground state is a spin forbidden process. Moreover, it is worthwhile noting that Sauvage and co-workers [31,44,45] as well as others [30,46] have developed molecular dyads and triads assembled around an iridium complex sensitizer which also lead to long-lived charge separated states (CSS) upon photoexcitation.…”

Section: Introductionmentioning

confidence: 99%

“Iridium effect” in cyclometalated iridium complexes for p-type dye sensitized solar cells

et al. 2019

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Cyclometallated iridium complexes have shown great promises as photosensitizers for p-type dye sensitized solar cells (p-DSSC), in particular due to the occurrence of very long-lived interfacial charge separated states, leading to high open circuit potentials (Voc). To rationalize this experimental fact, we prepared a new series of iridium photosensitizers specially designed for NiO based p-DSSC, in order to assess the role of a panel of factors on the overall photovoltaic performances. We probed the electronic coupling between the iridium complex and the semi-conductor at the level of the anchor, the importance of the frontier orbitals distribution over the photosensitizers structures and the impact of iridium(III) vs. a lighter metal ion like ruthenium(II). The synthesis and full characterizations of these new photosensitizers are presented, and their performances within p-type DSSC are given and discussed in light of their structures. A combination of a high spin-orbit coupling and a smart design of the anchoring ligands explains the interesting performances of iridium complexes as photosensitizers for p-DSSC.

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“…For instance, the ET kinetics dependency on the distance, or the electronic coupling magnitude between the donor (D) and acceptor (A) were systematically studied [12–14] . Methods for molecular structural design to prolong the CS state lifetimes were proposed, such as to reduce the electronic coupling, or by using the Marcus inverted region effect for the charge recombination (CR) process [13–16] . During last decade, however, some new topics have been fostered in this area.…”

Section: Introductionmentioning

confidence: 99%

Recent Developments on Understanding Charge Transfer in Molecular Electron Donor‐Acceptor Systems

et al. 2023

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Charge transfer (CT) in molecular electron donor-acceptor systems is pivotal for artificial photosynthesis, photocatalysis, photovoltaics and fundamental photochemistry. We summarized the recent development in study of CT and discussed its application in thermally activated delayed fluorescence (TADF) emitters. The direct experimental proof of the spin multiplicity of the charge separated (CS) state with pulsed laser excited time-resolved electron paramagnetic resonance (TREPR) spectroscopy was discussed. Experimental determination of the electron exchange energy (J) of the CS state, with magnetic field effect on its yield or lifetime was introduced. The electron spin transfer accompanying the CT, studied with pulsed EPR spectra was briefly discussed. Tuning of the CT yield and kinetics with selective vibration excitation of the linker (the bridge) with IR pulse was presented. Above all, these studies show that there are more fun than simply monitoring the formation of the cations and anions and the kinetics or CS yields in this area.

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Remarkable Dependence of the Final Charge Separation Efficiency on the Donor–Acceptor Interaction in Photoinduced Electron Transfer

Cited by 27 publications

References 28 publications

Symmetry-Breaking Charge Separation in Molecular Constructs for Efficient Light Energy Conversion

Symmetry-Breaking Charge Separation in Molecular Constructs for Efficient Light Energy Conversion

“Iridium effect” in cyclometalated iridium complexes for p-type dye sensitized solar cells

Recent Developments on Understanding Charge Transfer in Molecular Electron Donor‐Acceptor Systems

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