Tailoring intra-molecular coupling in BDT-based copolymers to enhance their performance in fullerene-free organic solar cells

Tegegne, Newayemedhin A.; Negash, Asfaw; Yilma, Desalegn; Gebremariam, Kidan G.; Genene, Zewdneh; Mammo, Wendimagegn; Goosen, Neill J.

doi:10.1039/d3ma00779k

Cited by 2 publications

(2 citation statements)

References 39 publications

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“…The dipole moments of the SAMs are expected to facilitate the development of an interfacial dipole at the interface between the ETL and the photoactive layer, possibly aiding charge transfer . Since the dipole moments of the SAMs are due to their electrostatic charge distribution, we further analyzed the electrostatic potential (ESP) of each atom in the SAMs using the Multiwfn 3.7 analyzer . This analysis provided insights into the ESP distribution across the terminal, spacer, and anchor groups of the SAMs as shown in Figure d.…”

Section: Resultsmentioning

confidence: 99%

“…30 Since the dipole moments of the SAMs are due to their electrostatic charge distribution, we further analyzed the electrostatic potential (ESP) of each atom in the SAMs using the Multiwfn 3.7 analyzer. 31 This analysis provided insights into the ESP distribution across the terminal, spacer, and anchor groups of the SAMs as shown in Figure 1d. The results revealed that the silane anchor group exhibits a much more negative ESP of −1.8 eV compared to the thiol group (−0.65 eV).…”

Section: ■ Introductionmentioning

confidence: 99%

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Self-Assembled Monolayer Engineered ZnO Electron Transport Layer to Improve the Photostability of Organic Solar Cells

Gebremariam,

Hone,

Negash

et al. 2024

Energy Fuels

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The degradation of organic solar cells (OSCs) can occur in any of the layers, underlining the importance of each layer in prolonging their lifetime. To enhance the performance and stability of inverted OSCs (i-OSCs), interfacial modification has been employed. In this context, two self-assembled monolayers (SAMs), namely, octadecanthiol (ODT) and octadecyltrimethoxysilane (OTMS), were utilized to effectively passivate typical surface defects in the ZnO electron transport layer (ETL). The SAM-treated ZnO films were found to be more hydrophobic, which reduced surface defects produced by adsorbed oxygen and hydroxyl groups. Consequently, the power conversion efficiency (PCE) of the i-OSCs comprising an indacenodithieno[3,2-b]thiophene-alt-5,5-di(thiophen-2-yl)-2,2-bithiazole (PIDTT-DTBTz) donor blended with [6,6]-phenyl-C 71 -butyric acid methyl ester (PC 70 BM) acceptor increased from 4.20% in pristine ZnO-to 5.01 and 5.37% in ODTand OTMS-treated ZnO-based devices, respectively. In addition, the photostability of the device substantially improved. Hence, devices based on ZnO treated with ODT and OTMS kept 76 and 89% of their initial PCE, respectively, while pristine ZnO-based devices retained only 66% of the initial PCE after 48 h of irradiation. The improved PCE and extended lifetime of the i-OSCs can be attributed to enhanced charge transfer, the reduction in both bimolecular and trap-assisted recombination processes, and the enhanced interface between the ETL and the active layer. Moreover, it has been observed that the OTMS-treated ZnO ETL-based i-OSC offers better stability and more efficient devices compared to the ODT-treated ZnO ETL-based devices. This can be attributed to the favorable dipole moment generated by the increased electrostatic potential at the anchor group, which promotes improved device performance.

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Section: Resultsmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

Self-Assembled Monolayer Engineered ZnO Electron Transport Layer to Improve the Photostability of Organic Solar Cells

Gebremariam,

Hone,

Negash

et al. 2024

Energy Fuels

Self Cite

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Conformation-Dictated Aggregation Photophysics in Isoindigo-Based Copolymers

Asmare,

Bekri,

Nchinda

et al. 2024

J. Phys. Chem. C

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The aggregation of polymer chains directly influences the morphology of thin films used in optoelectronic devices. Therefore, understanding the relationship between the backbone conformation and aggregation of conjugated polymers is essential for ensuring optimal electronic performance. In this work, we study the effect of the backbone conformation on the aggregation photophysics of isoindigo-based copolymers, namely, bithiophene-isoindigo (P2TI) and thienothiophene-spaced bithiophene-isoindigo (P2TITT). The latter was systematically tuned by inserting thieno[3,2-b]thiophene (TT) into the former. Modification of the backbone by inserting TT was found to affect the planarity due to reduced steric hindrance between the donor and acceptor units. This reduced steric hindrance was further evidenced by the difference in the oscillator strength of the first excited-state transition, identified as an intramolecular charge transfer transition in time-dependent density functional theory (TD/DFT) calculations. Temperature-dependent photoluminescence (PL) of the two polymers was well reproduced using two Franck−Condon progressions, indicating the formation of both H-and J-type aggregates. This was supported by the presence of two emission lifetimes obtained from time-resolved fluorescence measurements. The evolution of the first two vibronic peaks with temperature clearly showed a stronger interchain interaction in P2TITT.

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Tailoring intra-molecular coupling in BDT-based copolymers to enhance their performance in fullerene-free organic solar cells

Cited by 2 publications

References 39 publications

Self-Assembled Monolayer Engineered ZnO Electron Transport Layer to Improve the Photostability of Organic Solar Cells

Self-Assembled Monolayer Engineered ZnO Electron Transport Layer to Improve the Photostability of Organic Solar Cells

Conformation-Dictated Aggregation Photophysics in Isoindigo-Based Copolymers

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