Uphill and downhill charge generation from charge transfer to charge separated states in organic solar cells

Energy level alignments at the organic donor–acceptor interface cannot be predicted from cyclic voltammetry. Onsets for joint density of states and charge generation, reveal cases of energy uphill and – newly observed – downhill charge generation.

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Long-lived and disorder-free charge transfer states enable endothermic charge separation in efficient non-fullerene organic solar cells

Nature Communications ◽

10.1038/s41467-020-19332-5 ◽

2020 ◽

Vol 11 (1) ◽

Cited By ~ 1

Author(s):

Ture F. Hinrichsen ◽

Christopher C. S. Chan ◽

Chao Ma ◽

David Paleček ◽

Alexander Gillett ◽

...

Keyword(s):

Solar Cells ◽

Charge Transfer ◽

Organic Solar Cells ◽

Charge Separation ◽

Free Charge ◽

Charge Generation ◽

Time Resolved ◽

Thermodynamic Conditions ◽

Donor Acceptor ◽

Interfacial Charge

Abstract Organic solar cells based on non-fullerene acceptors can show high charge generation yields despite near-zero donor–acceptor energy offsets to drive charge separation and overcome the mutual Coulomb attraction between electron and hole. Here, we use time-resolved optical spectroscopy to show that free charges in these systems are generated by thermally activated dissociation of interfacial charge-transfer states that occurs over hundreds of picoseconds at room temperature, three orders of magnitude slower than comparable fullerene-based systems. Upon free electron–hole encounters at later times, both charge-transfer states and emissive excitons are regenerated, thus setting up an equilibrium between excitons, charge-transfer states and free charges. Our results suggest that the formation of long-lived and disorder-free charge-transfer states in these systems enables them to operate closely to quasi-thermodynamic conditions with no requirement for energy offsets to drive interfacial charge separation and achieve suppressed non-radiative recombination.

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Synergistic Effect Incorporating Intra- and Inter-Molecular Charge Transfer in Nonfullerene Acceptor Molecules for High-Efficient Organic Solar Cells

Journal of Materials Chemistry A ◽

10.1039/d1ta01679b ◽

2021 ◽

Author(s):

Yiwen Ji ◽

Lingxia Xu ◽

Hang Yin ◽

Bin Cui ◽

Longlong Zhang ◽

...

Keyword(s):

Solar Cells ◽

Charge Transfer ◽

Organic Solar Cells ◽

Specific Mechanism ◽

Charge Generation ◽

High Efficient ◽

Molecular Charge ◽

Efficient Charge ◽

Donor Acceptor ◽

Nonfullerene Acceptor

Organic solar cells (OSCs) based on nonfullerene acceptors (NFAs) have achieved rapid developments benefiting from the near-zero donor/acceptor (D/A) energy offset. However, a specific mechanism underlying the high-efficient charge generation...

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Energy level alignment in polymer organic solar cells at donor-acceptor planar junction formed by electrospray vacuum deposition

Applied Physics Letters ◽

10.1063/1.4873164 ◽

2014 ◽

Vol 104 (16) ◽

pp. 163303 ◽

Cited By ~ 6

Author(s):

Ji-Hoon Kim ◽

Jong-Am Hong ◽

Dae-Gyeon Kwon ◽

Jaewon Seo ◽

Yongsup Park

Keyword(s):

Solar Cells ◽

Energy Level ◽

Organic Solar Cells ◽

Vacuum Deposition ◽

Energy Level Alignment ◽

Donor Acceptor ◽

Planar Junction

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Charge generation mediated by bound polaron pairs and delocalized charge transfer states in non-fullerene organic solar cells

The 22nd International Conference on Ultrafast Phenomena 2020 ◽

10.1364/up.2020.th2a.7 ◽

2020 ◽

Author(s):

Yin Song ◽

Xiao Liu ◽

Yongxi Li ◽

Hoang Huy Nguyen ◽

Rong Duan ◽

...

Keyword(s):

Solar Cells ◽

Charge Transfer ◽

Organic Solar Cells ◽

Charge Generation ◽

Bound Polaron

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Effect of Band Bending and Energy Level Alignment at the Donor/Acceptor Interface on Open-Circuit Voltage in Organic Solar Cells

The Journal of Physical Chemistry Letters ◽

10.1021/acs.jpclett.8b01134 ◽

2018 ◽

Vol 9 (11) ◽

pp. 2914-2918 ◽

Cited By ~ 12

Author(s):

Seiichiro Izawa ◽

Naoto Shintaku ◽

Masahiro Hiramoto

Keyword(s):

Solar Cells ◽

Energy Level ◽

Organic Solar Cells ◽

Open Circuit Voltage ◽

Open Circuit ◽

Band Bending ◽

Energy Level Alignment ◽

Donor Acceptor

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Design and characteration of planar star-shaped oligomer electron donors for organic solar cells: a DFT study

Canadian Journal of Chemistry ◽

10.1139/cjc-2015-0096 ◽

2015 ◽

Vol 93 (11) ◽

pp. 1181-1190 ◽

Cited By ~ 1

Author(s):

Dongmei Wang ◽

Zhiyuan Geng

Keyword(s):

Density Functional Theory ◽

Solar Cells ◽

Charge Transfer ◽

Energy Level ◽

Organic Solar Cells ◽

Density Functional ◽

Short Circuit ◽

Frontier Molecular Orbital ◽

Orbital Energy ◽

Functional Theory

To seek high-performance oligomer donor materials used in organic solar cells, four star-shaped molecules with a planar donor core derived from the recent reported molecule 3T-P-DPP (phenyl-1,3,5-trithienyl-diketopyrrolopyrrole) were designed. The molecular properties affecting the cell performance, such as structural characteristics, frontier molecular orbital energy level, absorption spectra, exciton character, and charge transfer/transport, were investigated by means of the density functional theory and time-dependent density functional theory methods. Comparative analysis showed that the new designed molecule 3 with a TTT (2,4,6-tri(thiophen-2-yl)-1,3,5-triazine) core has better planarity, a lower HOMO energy level, and a higher absorption efficiency, as well as more favorable exciton dissociation and charge transfer than the others, potentially improving the open-circuit voltage and short-circuit current density. Consequently, 3 maybe superior to 3T-P-DPP and may act as a promising donor material candidate for organic solar cells.

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