Forced coplanarity of dithienofluorene-based non-fullerene acceptors to achieve high-efficiency organic solar cells

Cao, Fong Yi; Huang, Po Kai; Su, Yen Chen; Huang, Wen; Chang, Shao Ling; Hung, Kai En; Cheng, Yen Ju

doi:10.1039/c9ta05116c

Cited by 17 publications

(9 citation statements)

References 82 publications

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“…Both DTG-IW and DTG-OW exhibited a clear melting transition during the heating cycle, as shown in Figure S2 and Table S1. Interestingly, compared with DTG-IW (melting temperature ( T m ) = 199.2 °C, enthalpy (Δ H m ) = 11.27 J g –1 ), DTG-OW exhibited higher T m (296.2 °C) and Δ H m (33.16 J g –1 ) values, indicating that the outward-directed side chains on the backbone strengthened the molecular ordering. ,− …”

Section: Resultsmentioning

confidence: 98%

Dithienogermole-Based Nonfullerene Acceptors: Roles of the Side-Chains’ Direction and Development of Green-Tinted Efficient Semitransparent Organic Solar Cells

Cho

Lee

Jeong

et al. 2020

ACS Appl. Energy Mater.

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Inspired by the encouraging properties of Ge-fused heterocyclic dithienogermole (DTG) in optoelectronic applications, we here report two narrow-bandgap acceptor−donor′−donor− donor′−acceptor (A−D′−D−D′−A)-type isomeric nonfullerene acceptors based on DTG (DTG-IW with inward-facing side chains vs DTG-OW with outward-facing side chains) for use in organic solar cells (OSCs). The introduction of the inward-facing side chains into the backbone results in extremely confined face-on crystallites in the solid state, as verified by grazing-incidence wideangle X-ray scattering measurements. This result is attributed mainly to a better power conversion efficiency (PCE) of 9.16% in the OSC based on a blend of DTG-IW with a narrow-bandgap PTB7-Th donor polymer, as compared with the corresponding DTG-OWbased one. Furthermore, the appealing feature of the blend mixing of the narrow-bandgap donor and acceptor pair is that it enables the construction of a green-tinted efficient semitransparent OSC with a PCE of 6.19% and transmittance of 50.4% in the green wavelength region through incorporation of the recently formulated semitransparent Ag/Sb 2 O 3 /Ag electrode. Overall, in addition to providing useful perspectives into the side-chain engineering of nonfullerene acceptors, this work highlights that OSC based on the A−D′−D−D′−A-type DTG is a promising narrow-bandgap acceptor for further improvement of the performance of semitransparent OSCs.

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Section: Resultsmentioning

confidence: 98%

Dithienogermole-Based Nonfullerene Acceptors: Roles of the Side-Chains’ Direction and Development of Green-Tinted Efficient Semitransparent Organic Solar Cells

Cho

Lee

Jeong

et al. 2020

ACS Appl. Energy Mater.

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“…(2) ZnO or ZSME layer formation: Methanol solutions of 2-DMAP (1:1 v% to MeOH) and PAS (1 mg/mL MeOH) were spin-cast on ITO glass at 4000 rpm, respectively, to form the ZSME layers. The ZnO layer was prepared as described previously . Furthermore, the blending solutions were spin-coated on top of ITO, ITO/ZnO, ITO/2-DMAP, and ITO/PAS and the detailed conditions are presented in Table S2.…”

Section: Experimental Methodsmentioning

confidence: 99%

“…The ZnO layer was prepared as described previously. 25 Furthermore, the blending solutions were spin-coated on top of ITO, ITO/ZnO, ITO/2-DMAP, and ITO/PAS and the detailed conditions are presented in Table S2. Finally, the hole-transporting layer of MoO 3 (7 nm) and anode of silver (150 nm) were deposited by thermal evaporation.…”

Section: Experimental Methodsmentioning

confidence: 99%

“…Organic solar cells (OSCs) have attracted considerable research interest due to their superior properties such as lightweight, flexibility, semitransparency, and solution process availability. − In the past few years, the n-type materials applied in bulk-heterojunction (BHJ) solar cells have been gradually shifted from fullerene-based acceptors to acceptor–donor–acceptor (A–D–A)-type nonfullerene acceptors (NFAs), which possess strong light-harvesting ability and tunable HOMO/LUMO energy levels. − Compared to the fullerene-based OSCs, the A–D–A-type NFAs dramatically improve short-circuit current density ( J sc ) and open-circuit voltage ( V oc ), − leading to power conversion efficiencies (PCE) over 17% in a single-junction device. , Inverted OSC (I-OSC) using a high-work-function Ag as the anode is generally considered to have better device air stability without encapsulation. Insertion of an electron-transporting zinc oxide (ZnO) layer between ITO and active layer in an I-OSC device is essential to enhance the electron extraction and transport. , The preparation of high-quality ZnO layer by the sol–gel process is highly crucial.…”

Section: Introductionmentioning

confidence: 99%

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Alcohol-Soluble Zwitterionic 4-(Dimethyl(pyridin-2-yl)ammonio)butane-1-sulfonate Small Molecule as a Cathode Modifier for Nonfullerene Acceptor-Based Organic Solar Cells

Cao

Hsueh

et al. 2021

ACS Appl. Mater. Interfaces

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A new zwitterionic small molecule 4-(dimethyl(pyridin-2-yl)ammonio)butane-1-sulfonate (PAS), synthesized from 2-dimethylaminopyrindine (2-DMAP), was developed for the ITO cathode modifier. PAS and 2-DMAP dissolved in methanol can form a thin layer on ITO cathode by a simple spin-coating process. The heteroatom moieties in 2-DMAP (sp2 and sp3 nitrogen) and PAS (sp2 nitrogen and sulfonate ion) can coordinate to the ITO surface and decrease the ITO work function by the induced surface dipoles. The fullerene-based (PBDTT-FTTE:PC71BM) inverted OSCs using PAS and 2-DMAP interlayer can achieve PCEs of 8.95 and 8.26%, respectively, which are superior to the devices without a modifier (PCE = 3.25%) and comparable to the corresponding ZnO-based device (PCE = 8.57%). Nevertheless, 2-DMAP, like other nitrogen-containing polymer interlayer materials, turns out to be not applicable to inverted organic solar cells (I-OSCs) with IT-4F as the n-type electron acceptor because the amino group of 2-DMAP can act as a nucleophile to attack the end-group of IT-4F at the interface. The decomposition of IT-4F by 2-DMAP was carefully proved to be via retro-aldol condensation. As a result, the device (PBDBT-F:IT-4F) modified with 2-DMAP displayed a low PCE of 7.34%. The zwitterionic PAS with reduced nucleophilicity and basicity can modify the ITO surface without decomposing IT-4F. The PBDBT-F:IT-4F-based device modified with PAS maintained a high PCE of 11.41%. Most importantly, the PAS-based device using the well-known Y6 acceptor (PBDBT-F:Y6) can achieve a PCE of 13.82%. This new interfacial material can be universally applied to I-OSCs employing various A–D-A-type acceptors installed with the electrophilic 1,1-dicyanamethylene-5,6-difluoro-3-indanone (FIC) end-group.

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“…Cheng et al 94 synthesized an extremely planar NFA, incorporating two carbon bridges to fasten the central DTF core with two outer thiophene rings, forming a new laddertype nonacyclic dithieno[3,2-b:6,7-b′] fluorenedi(cyclopentathiophene) (denoted as DTFT9), which combined with a polymer donor, PBDB-T, resulting in an efficiency of 9.58%. And DTFT9 was further condensed with two FIC acceptor units (FIC, 1,1-dicyanomethylene-5,6-diuoro-3-indanone) to yield a carbon-bridged DTFT9-FIC.…”

Section: Mending Charge Dynamicsmentioning

confidence: 99%

High-Performance Ternary Organic Solar Cells Enabled by Synergizing Fullerene and Non-fullerene Acceptors

Jiang

Zhu

2021

Organic Materials

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With the development of the non-fullerene acceptor (NFA), the use of ternary organic photovoltaic devices based on a fullerene acceptor and a NFA is now widespread, and the merits of both acceptor types can be fully utilized. However, the effective approach of enhancing device performance is adjusting the charge dynamics and the thin-film morphology of the active layer via introducing the second acceptor, which would significantly impact the open-circuit voltage, the short-circuit current, and the fill factor, thus strongly affecting device efficiency. The functions of the second acceptor in a ternary organic solar cell with a fullerene acceptor and a NFA are summarized here. These include a broader absorption spectrum; formation of a cascade energy level or energy transfer; modified thin-film morphology including phase separation, effects on crystallinity, size, and purity of domain; and vertical distribution along with improved charge dynamics like exciton dissociation and charge transport, collection, and recombination. Then, we discuss the hierarchical morphology in ternary solar cells may benefit device performance and the outlook of the ternary device.

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Forced coplanarity of dithienofluorene-based non-fullerene acceptors to achieve high-efficiency organic solar cells

Abstract: This work clearly demonstrates the importance of chemical planarization in designing high-performance nonfullerene acceptors and the ternary-blend device using PBDB-T:DTFT9-FIC:PC71BM achieved a high PCE of 11.82%.

Cited by 17 publications

References 82 publications

Dithienogermole-Based Nonfullerene Acceptors: Roles of the Side-Chains’ Direction and Development of Green-Tinted Efficient Semitransparent Organic Solar Cells

Dithienogermole-Based Nonfullerene Acceptors: Roles of the Side-Chains’ Direction and Development of Green-Tinted Efficient Semitransparent Organic Solar Cells

Alcohol-Soluble Zwitterionic 4-(Dimethyl(pyridin-2-yl)ammonio)butane-1-sulfonate Small Molecule as a Cathode Modifier for Nonfullerene Acceptor-Based Organic Solar Cells

High-Performance Ternary Organic Solar Cells Enabled by Synergizing Fullerene and Non-fullerene Acceptors

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