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1.
Artigo em Inglês | MEDLINE | ID: mdl-33373184

RESUMO

The rapid advance of fused-ring electron acceptors (FREAs) has made them a potential substitute to fullerene-based acceptors and offered new avenues for the construction of organic solar cells (OSCs). Nonfused-ring acceptors (NFRAs) could significantly reduce the synthetic cost while achieving reasonable power conversion efficiencies (PCEs). Widely used fullerene acceptors have been applied as a second acceptor to regulate the morphology, absorption, and electron transport. To take full advantage of both nonfullerene and fullerene acceptors at the same time, we rationally designed and synthesized two novel NFRAs with phenyl-C61-butyric acid methyl ester (PCBM) as the lateral pendent. With the incorporation of fullerene pendent in PCBM-C6 and PCBM-C10, varied UV-vis absorption and photoluminescence (PL) quenching behaviors were observed, and isotropic diffraction patterns were obtained via grazing incidence wide-angle X-ray scattering (GIWAXS) measurements. The bulky, spherical, and electronic isotropic fullerene pendent could effectively suppress severe molecular aggregation and form the preferred blend morphology. This strategy significantly improved the efficiencies for exciton separation and charge collection relative to the control acceptor CH3COO-C6. Finally, the Voc, Jsc, and fill factor (FF) of PCBM-C10-based devices were simultaneously improved and an enhanced PCE of 13.55% was accomplished.

2.
Chem Commun (Camb) ; 2020 Dec 21.
Artigo em Inglês | MEDLINE | ID: mdl-33346281

RESUMO

Organic semiconductors including conjugated polymers and small molecules can be applied in many fields due to their unique advantages, such as light weight, solution processability, easy functionalization etc. During the past ten years, we mainly focused on the design and synthesis of conjugated polymer donor materials and small molecular acceptor materials for organic solar cells and hole transport materials for perovskite solar cells. To obtain planar conjugated polymers, low cost small molecular acceptors, and dopant-free hole transport polymers, we adopted intramolecular noncovalent interactions (INCIs) as the design strategy. In this brief review, we will demonstrate that the INCI strategy is very efficient in the design of high performance photovoltaic materials.

3.
Adv Mater ; : e2003164, 2020 Nov 09.
Artigo em Inglês | MEDLINE | ID: mdl-33164236

RESUMO

Exciton lifetime (τ) is crucial for the migration of excitons to donor/acceptor interfaces for subsequent charge separation in organic solar cells (OSCs); however, obvious prolongation of τ has rarely been achieved. Here, by introducing a solid additive 9-fluorenone-1-carboxylic acid (FCA) into the active layer, which comprises a nonfullerene acceptor, 3,9-bis(2-methylene-((3-(1,1-dicyanomethylene)-6/7-methyl)-indanone))-5,5,11,11-tetrakis(4-hexylphenyl)-dithieno[2,3-d:2',3'-d']-s-indaceno[1,2-b:5,6-b']dithiophene (IT-M), τ is substantially prolonged from 491 to 928 ps, together with obvious increases in fluorescence intensity and quantum yield. Time-resolved transient infrared spectra indicate the presence of an intermolecular vibrational coupling between the electronic excited state of IT-M and the electronic ground state of FCA, which is first observed here and which can suppress the internal conversion process. IT-M-based OSCs display an improved short-circuit current and fill factor after the addition of FCA. Thus, the power conversion efficiency is increased, particularly for devices with a large donor/acceptor ratio of 1:4, whose efficiency is increased by 56%. This study describes a novel method, which is also applicable to other nonfullerene acceptors, for further improving the performance of OSCs without affecting their morphology and light absorption properties.

4.
ACS Appl Mater Interfaces ; 12(47): 53021-53028, 2020 Nov 25.
Artigo em Inglês | MEDLINE | ID: mdl-33170610

RESUMO

As a well-known electron-withdrawing group, benzo[c][1,2,5]thiadiazole (BT) has been intensively studied and adopted to construct polymer donors with tunable band gaps. However, polymer solar cells (PSCs) with BT-based polymer donors, limited by the weak absorption and inflexible energy level of fullerene derivatives, usually suffer mediocre power conversion efficiencies (PCEs). Here, through subtly tailoring a BT unit with asymmetric fluoro and alkyloxy groups and judiciously pairing a BT-based polymer donor with three narrow band gap non-fullerene acceptors (e.g., IEICO-4F, ITOIC-2F, and IDTCN-O), active layers with complementary absorption spectra, small lowest unoccupied molecular orbital (LUMO) offsets, and preferred morphologies have been achieved. Consequently, PSCs with excellent Jsc values (over 20 mA/cm2) and high PCEs up to 12.33% have been obtained. To the best of our knowledge, the value of 12.33% is among the highest PCEs for BT-based polymers in binary PSCs so far. This work demonstrates that the cooperative effect of energy levels, absorption spectra, and morphologies between the donors and acceptors is crucial for governing the performance of organic photovoltaics.

5.
Angew Chem Int Ed Engl ; 59(50): 22714-22720, 2020 Dec 07.
Artigo em Inglês | MEDLINE | ID: mdl-32866327

RESUMO

Fused-ring electron acceptors have made significant progress in recent years, while the development of fully non-fused ring acceptors has been unsatisfactory. Here, two fully non-fused ring acceptors, o-4TBC-2F and m-4TBC-2F, were designed and synthesized. By regulating the location of the hexyloxy chains, o-4TBC-2F formed planar backbones, while m-4TBC-2F displayed a twisted backbone. Additionally, the o-4TBC-2F film showed a markedly red-shifted absorption after thermal annealing, which indicated the formation of J-aggregates. For fabrication of organic solar cells (OSCs), PBDB-T was used as a donor and blended with the two acceptors. The o-4TBC-2F-based blend films displayed higher charge mobilities, lower energy loss and a higher power conversion efficiency (PCE). The optimized devices based on o-4TBC-2F gave a PCE of 10.26 %, which was much higher than those based on m-4TBC-2F at 2.63 %, and it is one of the highest reported PCE values for fully non-fused ring electron acceptors.

6.
ACS Appl Mater Interfaces ; 12(41): 46220-46230, 2020 Oct 14.
Artigo em Inglês | MEDLINE | ID: mdl-32938186

RESUMO

Four noncovalently fused-ring electron acceptors p-DOC6-2F, o-DOC6-2F, o-DOC8-2F, and o-DOC2C6-2F have been designed and synthesized. p-DOC6-2F and o-DOC6-2F have the same molecular backbone but different molecular shapes and symmetries. p-DOC6-2F has an S-shaped molecular backbone and C2h symmetry, whereas o-DOC6-2F possesses a U-shaped molecular backbone and C2v symmetry. The molecular shape and symmetry can influence the dipole moment, solubility, optical absorption, energy level, molecular packing, and film morphology. Compared with the corresponding p-DOC6-2F, o-DOC6-2F exhibits better solubility, a wider band gap, and a larger dipole moment. When blended with the donor polymer PBDB-T, the C2v symmetric o-DOC6-2F can form an appropriate active layer morphology, whereas the C2h symmetric p-DOC6-2F forms oversized domains. Organic solar cells (OSCs) based on p-DOC6-2F, o-DOC6-2F, o-DOC8-2F, and o-DOC2C6-2F obtained power conversion efficiencies of 9.23, 11.87, 11.23, and 10.80%, respectively. The result reveals that the molecular symmetry can facilely regulate the performance of OSCs.

7.
ACS Appl Mater Interfaces ; 12(36): 40590-40598, 2020 Sep 09.
Artigo em Inglês | MEDLINE | ID: mdl-32805919

RESUMO

In this work, a ternary blend strategy based on PBDB-T and two small molecular acceptors (IDTT-OB and IDT-PDOT-C6) is demonstrated to simultaneously improve the photocurrent and reduce the voltage loss in organic solar cells (OSCs). The improved photocurrent is partially due to a broad absorption spectrum of the active layer. In addition, we find that the ternary system possesses a higher degree of crystallinity, smaller domain size, higher domain purity, and higher and more balanced charge-carrier mobilities in comparison with the two corresponding binary systems. The reduced voltage loss in the ternary device is mainly due to a lower energy loss (Eloss) of charge carriers. We achieve a Eloss of only 0.50 eV, which is one of the lowest values reported for the ternary nonfullerene OSCs. Our results have demonstrated that all photovoltaic parameters of ternary OSCs can be simultaneously improved by elaborately selecting the three active layer components.

8.
ACS Appl Mater Interfaces ; 12(33): 37409-37417, 2020 Aug 19.
Artigo em Inglês | MEDLINE | ID: mdl-32814394

RESUMO

Three hexapod-shaped PDI-hexamers (PSM1, PSM2, and PSM3) with a diphenylmethylene-bridged triphenylamine (TPA) core and six peripheral PDI subunits have been designed and synthesized. The influence of different peripheral PDI subunits on the morphology and crystallinity of acceptors is investigated. Distinctly different from the previously reported PDI trimers with a TPA core, which exhibit amorphous morphologies, these hexapod-shaped acceptors display improved crystallinities and photophysical properties. Our studies have shown that PSM3 with six peripheral thiophene-fused PDI subunits gives the best result. The as-cast blend films of PBDB-T and PSM3, which possess appropriate phase separation and higher crystallinity, show high and balanced charge mobilities. As expected, OSCs with PBDB-T:PSM3 as the active layer achieve the highest power conversion efficiency of 6.71% among these three acceptors, which is the highest one in TPA-based acceptors and one of the best for the as-cast OSCs based on PDI derivatives.

9.
Angew Chem Int Ed Engl ; 59(45): 20161-20166, 2020 Nov 02.
Artigo em Inglês | MEDLINE | ID: mdl-32710517

RESUMO

Herein, norbornyl (NB), a bulky annular nonconjugated spacer, is melded into π systems to construct two groups of ladder-type room-temperature phosphorescence (RTP) luminogens. The effect of the NB on π-π interactions, packing modes and RTP performance is explored systematically. The experimental and computational results demonstrate the versatility of NB in reducing π-π distances and synergistically intensifying the intermolecular interactions, which not only induces intersystem crossing from S1 to Tn but also diminishes the nonradiative decay of triplet excitons. Impressively, 1800-fold phosphorescence lifetime enhancement is achieved in comparison with the reference compounds without NB. The molecular packing and RTP performance can be further modulated by the length of the backbones and terminal end-groups. It is quite peculiar that NB-annulated phthalic acid exhibits reversible photochromism in the solid state, likely due to the formation of persistent radical pairs. Our study paves an ingenious avenue towards enhancing intermolecular interactions and provides significant implications for a better comprehensive understanding of the origin of their RTP and the inherent photophysical mechanism.

10.
ACS Appl Mater Interfaces ; 12(9): 10746-10754, 2020 Mar 04.
Artigo em Inglês | MEDLINE | ID: mdl-32054268

RESUMO

We designed and synthesized two non-fullerene acceptors (CDT-TFP and C8X-TFP), which comprise a central 4H-cyclopenta[2,1-b:3,4-b']dithiophene (CDT) as the bridge and two thiophene-fused perylene diimide (TFP) units. The bulky side chains, such as the 4-hexylphenyl side chains, on the CDT bridge can effectively prevent the acceptor molecules from forming large aggregates, and the π-π stacking of the terminal planar TFP units can form effective electron transport pathways when blending with the donor polymers. These non-fullerene acceptors are used to fabricate organic solar cells (OSCs) by blending with the regioregular middle bandgap polymer reg-PThE. The as-cast devices based on reg-PThE:CDT-TFP show the best power conversion efficiency (PCE) of 8.36% with a Voc of 1.10 V, Jsc of 12.43 mA cm-2, and an FF of 61.4%, whereas the analogue perylene diimide (PDI) dimers (CDT-PDI) that comprise two PDI units bridged with a CDT unit show only a 2.59% PCE with a Voc of 0.92 V, Jsc of 6.82 mA cm-2, and an FF of 41.5%. Our results have demonstrated that the non-fullerene acceptors comprising planar PDI units can achieve excellent photovoltaic performance and provide meaningful guidelines for the design of PDI-based non-fullerene electron acceptors for efficient OSCs.

11.
ACS Appl Mater Interfaces ; 12(4): 4638-4648, 2020 Jan 29.
Artigo em Inglês | MEDLINE | ID: mdl-31903738

RESUMO

Three noncovalently fused-ring electron acceptors (FOC6-IC, FOC6-FIC, and FOC2C6-2FIC) are synthesized. Single crystals of FOC6-IC and FOC2C6-2FIC are prepared, and structure analyses reveal that the molecular backbone can be planarized via the formation of the intramolecular noncovalent interactions. These acceptor molecules can be packed closely in the solid state via π-π stacking and static interactions between the central phenylene unit and the terminal group with a distance of 3.3-3.4 Å. Besides, multiple intermolecular noncovalent interactions can be observed in the single crystal structure of the fluorinated acceptor FOC2C6-2FIC, which help increase the crystallinity of acceptors and the charge mobility of the blends. Photovoltaic devices based on FOC2C6-2FIC give a power conversion efficiency of 12.36%, higher than 12.08% for FOC6-FIC and 10.80% for FOC6-IC.

12.
ACS Appl Mater Interfaces ; 12(4): 4887-4894, 2020 Jan 29.
Artigo em Inglês | MEDLINE | ID: mdl-31898889

RESUMO

We precisely design and synthesize two A-π-D-π-A type dipyran-cored nonfullerene acceptors (NFAs) Ph-DTDPo-OT and Ph-DTDPi-OT with oxygen atoms at the outer and inner positions, respectively. 3-Hexyloxythiophene is used as the π-spacer to expand the effective conjugation length of the acceptors. These two NFAs possess similar optical band gaps and energy levels. However, the position of the oxygen atom at the dipyran core can markedly influence the molecular packing and aggregation behavior of the resulted acceptors. Ph-DTDPo-OT with a strong intermolecular affinity tends to form larger aggregates blending with PBDB-T, leading to a lower photovoltaic performance; Ph-DTDPi-OT presents good miscibility with PBDB-T and the blend films preferentially adopt a face-on orientation. Ph-DTDPi-OT-based devices display high and balanced hole and electron mobilities, leading to an optimal power conversion efficiency of 11.38%, which is much higher than those of Ph-DTDPo-OT-based ones (7.60%). Moreover, Ph-DTDPi-OT-based devices also exhibit a lower nonradiative recombination voltage loss of 0.268 eV. Our work demonstrates that the π-spacer and chemical structure of the core unit can greatly influence the molecular packing and the morphology of blend films, which are critical to the photovoltaic performance of devices.

13.
Nat Commun ; 10(1): 3038, 2019 Jul 10.
Artigo em Inglês | MEDLINE | ID: mdl-31292441

RESUMO

Non-fullerene fused-ring electron acceptors boost the power conversion efficiency of organic solar cells, but they suffer from high synthetic cost and low yield. Here, we show a series of low-cost noncovalently fused-ring electron acceptors, which consist of a ladder-like core locked by noncovalent sulfur-oxygen interactions and flanked by two dicyanoindanone electron-withdrawing groups. Compared with that of similar but unfused acceptor, the presence of ladder-like structure markedly broadens the absorption to the near-infrared region. In addition, the use of intramolecular noncovalent interactions avoids the tedious synthesis of covalently fused-ring structures and markedly lowers the synthetic cost. The optimized solar cells displayed an outstanding efficiency of 13.24%. More importantly, solar cells based on these acceptors demonstrate very low non-radiative energy losses. This research demonstrates that low-cost noncovalently fused-ring electron acceptors are promising to achieve high-efficiency organic solar cells.

14.
Front Chem ; 7: 333, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31157206

RESUMO

Fluorination of conjugated polymers is an effective strategy to tune the energy levels for obtaining high power conversion efficiency (PCE) in organic solar cells. In this work, we have developed fluoro-modulated molecular geometries in diketopyrrolopyrrole based low-bandgap copolymers. In these polymers, planar conformation can be locked by intramolecular non-covalent interaction (intramolecular supramolecular interaction) between the sulfur atoms and the introduced F atoms (F···S interaction). By varying the fluorinated moieties, such a planarity can be disturbed and the molecular geometry is tuned. As a result, the polymer' properties can be modulated, including the ultraviolet-visible absorption spectrum to become broaden, charge mobility to be enhanced, open-circuit voltage (V oc) and short-circuited current (J sc) to be elevated, and thus photovoltaic performance to be improved. The photovoltaic device based on PCFB, one of the fluorinated terpolymers, exhibited a high PCE near 8.5% with simultaneously enhanced V oc and J sc relative to the non-fluorinated one (PCB).

15.
ACS Appl Mater Interfaces ; 11(21): 19444-19451, 2019 May 29.
Artigo em Inglês | MEDLINE | ID: mdl-31060351

RESUMO

Two A-π-D-π-A-type non-fullerene acceptors (IDT-ToFIC and IDT-TiFIC) with 5-hexylthienyl chains substituted at the inner and outer ß-positions of the thiophene π-bridge have been designed, respectively. Impacts of varied positional modifications are systematically studied. By utilizing PBDB-T as the donor, polymer solar cells are constructed with these two molecules as acceptors. Power conversion efficiencies of 11.09 and 9.46% are acquired for IDT-ToFIC- and IDT-TiFIC-based devices, respectively. Our studies have demonstrated that the use of thiophene spacers carrying one conjugated side chain at different positions can markedly enhance the photovoltaic properties relative to the corresponding control molecule IDTT2F.

16.
ACS Appl Mater Interfaces ; 11(3): 3098-3106, 2019 Jan 23.
Artigo em Inglês | MEDLINE | ID: mdl-30585714

RESUMO

A nonfullerene acceptor, IDTT-OB, employing indacenodithieno[3,2- b]thiophene (IDTT) decorated with asymmetric substituents as the core, is designedly prepared. In comparison with the analogue IDT-OB, extending the five-heterocyclic indacenodithiophene (IDT) core to seven-heterocyclic fused ring endows IDTT-OB with more broad absorption and elevated highest occupied molecular orbital energy level. In addition, IDTT-OB shows a more intense molecular packing and a higher crystalline behavior with a strong face-on orientation in the neat film and the PBDB-T:IDTT-OB blend film. Furthermore, an ideal nanomorphology with a domain size of 19 nm can be obtained, which is in favor of exciton diffusion and charge separation. Accordingly, PBDB-T:IDTT-OB-based polymer solar cells demonstrate a maximum power conversion efficiency (PCEmax) of 11.19% with an impressive fill factor of 0.74, comparable to the state-of-the-art acceptors with similar molecular backbones. More importantly, IDTT-OB-based devices show good tolerance to the film thickness, which maintain a high PCE of 10.20% with a 250 nm thick active layer, demonstrating that the asymmetric acceptor is profound for fabricating high-efficiency thick-film nonfullerene solar cells.

18.
ACS Appl Mater Interfaces ; 10(37): 30919-30924, 2018 Sep 19.
Artigo em Inglês | MEDLINE | ID: mdl-30160097

RESUMO

Raising the light absorption of the photoactive layer in polymer solar cells (PSCs) without increasing the layer thickness is desirable but challenging because of the low carrier mobility of organic materials. Herein, we used the coupled localized surface plasmon resonance of heterostructured Au-Cu2- xS nanocrystals (NCs) to improve the light-trapping capability of the photoactive layer of PSCs. Broadband light absorption and a considerable improvement of the power conversion efficiency were obtained when the photoactive layer was doped with a tiny amount of NCs. This can be explicated by the enhanced near-field intensity and broadband scattering properties of added NCs.

19.
Nanoscale ; 10(25): 11745-11749, 2018 Jul 05.
Artigo em Inglês | MEDLINE | ID: mdl-29916503

RESUMO

Au-Cu2-xS Janus nanostructures with a shape-controlled semiconductor part are successfully built. The key parameters for controlling the morphology of Cu2-xS in Au-Cu2-xS are demonstrated. Coupled local surface plasmon resonance (LSPR) properties in these Au-Cu2-xS NCs give them potential for application in polymer solar cells (PSCs) as an efficient dopant.

20.
ACS Appl Mater Interfaces ; 10(16): 13931-13940, 2018 Apr 25.
Artigo em Inglês | MEDLINE | ID: mdl-29630335

RESUMO

A new centrosymmetrical dipyran unit (DTDP) is successfully prepared by means of an efficient and universal way, and a series of PDTDP polymers have been prepared so as to assess their potential application in organic photovoltaic. The function of pyran moiety is not merely limited to tune the electron-donating roles and energy levels but it also contributes to solubility improvement. Interestingly, all pyran-based polymers displayed wide absorption ranging from 350 to 780 nm, but varied aggregation phenomena are observed. Furthermore, the quantum chemistry calculations for dimers, morphology study and grazing-incidence wide-angle X-ray scattering analysis for blend films have been utilized to understand the variations at photovoltaic performances. Finally, PDTDP-4 achieved the highest power conversion efficiency of 7.26% ( Voc = 0.72 V, FF = 0.66, and Jsc = 15.30 mA/cm2), demonstrating promising usage for high-efficiency polymer donors in polymer solar cells. In all, not only a promising dipyran building block is provided by this study, more dipyran derivatives and polymers could be prepared via this facile synthetic route.

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