Tailoring the Energy Manifold of Quasi‐Two‐Dimensional Perovskites for Efficient Carrier Extraction

Ramesh, Sivarajan; Giovanni, David; Righetto, Marcello; Ye, Senyun; Fresch, Elisa; Wang, Yue; Collini, Elisabetta; Mathews, Nripan; Sum, Tze Chien

doi:10.1002/aenm.202103556

Cited by 19 publications

(37 citation statements)

References 61 publications

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“…In the ground state, the calculated DFT structures of Dp 15 and Dm ( diasteroisomer) (Figures S12-S13, Tables S4-S6) afford identical dihedral angles of 30º within the bridging ligand, both strongly deviated from planarity. 3 MLCT(bpy) states in Dp (which are not observed experimentally but exist) and Dm are also expected to have similar dihedral angles of 30º, because the bridging ligands are present in their non-reduced forms like in the ground state.…”

Section: Resultsmentioning

confidence: 98%

“…It is therefore of paramount importance to tame these dissipative pathways for efficient and optimal solar energy conversion schemes. To this end, dissipative processes in singlet fission 2 or in hot carrier solar cells 3 were previously explored. Ultimately, photosynthesis was re-wired to promote electron extraction directly from photoexcited photosystems, avoiding the electron transfer reaction chain which dissipates energy.…”

Section: Introductionmentioning

confidence: 99%

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Anti-dissipative strategies towards more efficient solar energy conversion

Cotic

Cerfontaine²,

Slep

et al. 2022

Preprint

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In natural and artificial photosynthesis, light absorption and catalysis are separate processes linked together by exergonic electron transfer. This leads to free energy losses between the initial excited state, formed after light absorption, and the catalytic center formed after the electron transfer cascade. Additional deleterious processes, such as internal conversion and vibrational relaxation, also dissipate as much as 20-30 % of the absorbed photon energy. Minimization of these energy losses, a holy-grail in solar energy conversion and solar fuels production, is a challenging task, because excited states are usually strongly coupled which results in negligible kinetic barriers and very fast dissipation. Here we show that topological control of oligomeric {Ru(bpy)3} chromophores resulted in small excited-state electronic couplings, leading to activation barriers for internal conversion of around 2000 cm–1 and effectively slowing down dissipation. Two types of excited states are populated upon visible light excitation, i.e. a bridging-ligand centered metal-to-ligand charge transfer (MLCTLm), and a 2,2’-bipyridine-centered MLCT (MLCTbpy), which lies 800-1400 cm–1 higher in energy. As a proof-of-concept, bimolecular electron transfer with tri-tolylamine as electron donor was performed, which mimics catalyst activation by sacrificial electron donors in typical photocatalytic schemes. Both excited states were efficiently quenched by tri-tolylamine and produced the corresponding bpy•– and Lm•– centered reduced complexes, as confirmed by transient absorption spectroscopy. This efficiently generated two distinct reduced photosensitizers with different reducing abilities, i.e. –0.93 V and –0.79 V vs NHE for bpy•– and Lm•–, respectively. Hence, this novel strategy not only allows to trap higher energy excited states, before internal conversion and vibrational relaxation set in, saving between 110 and 170 meV and but also leads in fine to 140 meV more potent reductant for energy conversion schemes and solar fuels production. These results lay the first stone for anti-dissipative energy conversion schemes which, in bimolecular electron transfer reactions, harnesses the excess energy saved by controlling dissipative conversion pathways.

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Section: Resultsmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

Anti-dissipative strategies towards more efficient solar energy conversion

Cotic

Cerfontaine²,

Slep

et al. 2022

Preprint

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show abstract

“…Molecular chromophores with retarded IC are analogous to hot carrier materials, where the excess energy of hot carriers can be extracted before cooling (heat transfer to the lattice) to band edge energies. 55 The next step is the development of molecular chromophores where IC is further retarded to the nanosecond timescale, compatible with bimolecular reactivity. Integration of these molecules and materials in anti-dissipation solar energy conversion schemes is a promising strategy to increase conversion efficiencies.…”

Section: Discussionmentioning

confidence: 99%

Unusually high energy barriers for internal conversion in a {Ru(bpy)} chromophore

Cotic

Veys

Escudero

et al. 2022

Phys. Chem. Chem. Phys.

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“…27−29 In this context, slow IC in the form of ILET or other electron transfers is very rare. For example, Huijser et al recently reported the population of two relaxed 3 MLCT excited states that behaved independently, implying a slow interconversion after incomplete ILET that takes 20 ps. 30,31 Our attention was focused on D p and D m (Figure 2), which are {Ru(bpy) 3 } dimers with outstanding properties in terms of light absorption, photostability, 32,33 and photoredox catalytic activity.…”

Section: ■ Introductionmentioning

confidence: 99%

Anti-Dissipative Strategies toward More Efficient Solar Energy Conversion

et al. 2023

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In natural and artificial photosynthesis, light absorption and catalysis are separate processes linked together by exergonic electron transfer. This leads to free energy losses between the initial excited state, formed after light absorption, and the active catalyst formed after the electron transfer cascade. Additional deleterious processes, such as internal conversion (IC) and vibrational relaxation (VR), also dissipate as much as 20−30% of the absorbed photon energy. Minimization of these energy losses, a holy grail in solar energy conversion and solar fuel production, is a challenging task because excited states are usually strongly coupled which results in negligible kinetic barriers and very fast dissipation. Here, we show that topological control of oligomeric {Ru(bpy) 3 } chromophores resulted in small excited-state electronic couplings, leading to activation barriers for IC by means of inter-ligand electron transfer of around 2000 cm −1 and effectively slowing down dissipation. Two types of excited states are populated upon visible light excitation, that is, a bridging-ligand centered metal-to-ligand charge transfer [MLCT(L m )], and a 2,2′-bipyridine-centered MLCT [MLCT(bpy)], which lies 800−1400 cm −1 higher in energy. As a proof-of-concept, bimolecular electron transfer with tri-tolylamine (TTA) as electron donor was performed, which mimics catalyst activation by sacrificial electron donors in typical photocatalytic schemes. Both excited states were efficiently quenched by TTA. Hence, this novel strategy allows to trap higher energy excited states before IC and VR set in, saving between 100 and 170 meV. Furthermore, transient absorption spectroscopy suggests that electron transfer reactions with TTA produced the corresponding L m •− -centered and bpy •− -centered reduced photosensitizers, which involve different reducing abilities, that is, −0.79 and −0.93 V versus NHE for L m•− and bpy •− , respectively. Thus, this approach probably leads in fine to a 140 meV more potent reductant for energy conversion schemes and solar fuel production. These results lay the first stone for anti-dissipative energy conversion schemes which, in bimolecular electron transfer reactions, harness the excess energy saved by controlling dissipative conversion pathways.

show abstract

Tailoring the Energy Manifold of Quasi‐Two‐Dimensional Perovskites for Efficient Carrier Extraction

Cited by 19 publications

References 61 publications

Anti-dissipative strategies towards more efficient solar energy conversion

Anti-dissipative strategies towards more efficient solar energy conversion

Unusually high energy barriers for internal conversion in a {Ru(bpy)} chromophore

Anti-Dissipative Strategies toward More Efficient Solar Energy Conversion

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