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1.
Artigo em Inglês | MEDLINE | ID: mdl-32946216

RESUMO

Efficient organic photovoltaics (OPVs) based on slot-die-coated (SD) ternary blends were developed for low-intensity indoor light harvesting. For active layers processed in air and from eco-friendly solvents, our device performances (under 1 sun and low light intensity) are the highest reported values for fluoro-dithiophenyl-benzothiadiazole donor polymer-based OPVs. The N-annulated perylene diimide dimer acceptor was incorporated into a blend of donor polymer (FBT) and fullerene acceptor (PC61BM) to give ternary bulk heterojunction blends. SD ternary-based devices under 1 sun illumination showed enhanced power conversion efficiency (PCE) from 6.8 to 7.7%. We observed enhancement in the short-circuit current density and open-circuit voltage of the devices. Under low light intensity light-emitting device illumination (ca. 2000 lux), the ternary-based devices achieved a PCE of 14.0% and a maximum power density of 79 µW/cm2 compared to a PCE of 12.0% and a maximum power density of 68 µW/cm2 for binary-based devices. Under the same illumination conditions, the spin-coated (SC) devices showed a PCE of 15.5% and a maximum power density of 88 µW/cm2. Collectively, these results demonstrate the exceptional promise of a SD ternary blend system for indoor light harvesting and the need to optimize active layers based on industry-relevant coating approaches toward mini modules.

2.
Chem Commun (Camb) ; 56(70): 10131-10134, 2020 Sep 11.
Artigo em Inglês | MEDLINE | ID: mdl-32812572

RESUMO

The synthesis of benzothioxanthene imide based dimers is reported herein. Subtle chemical modifications were carried out and their impact on the optical and electrochemical properties was investigated for a better structure-property relationship analysis. The icing on the cake was that these new structures were used as light emitting materials for the fabrication and demonstration of the first BTXI-based OLEDs.

3.
ACS Appl Mater Interfaces ; 11(49): 46017-46025, 2019 Dec 11.
Artigo em Inglês | MEDLINE | ID: mdl-31725265

RESUMO

Strong visible light absorption is essential to achieve high power conversion efficiency in indoor organic photovoltaics (iOPVs). Here, we report iOPVs that exhibit high efficiency with high voltage under excitation by low power indoor lighting. Inverted type organic photovoltaic devices with active layer blends utilizing the polymer donor PPDT2FBT paired with fullerene, perylene diimide, or ring-fused acceptors that are 6.5-9.1% efficient under 1 sun are demonstrated to reach efficiencies from 10 to 17% under an indoor light source. This performance transcends that of a standard silicon photovoltaic device. Moreover, we compared iOPVs with active layers both spin-cast and slot-die cast from nonhalogenated solvents and demonstrate comparable performance. This work opens a path towards high-efficiency iOPVs for low power electronics.

4.
ACS Appl Mater Interfaces ; 11(42): 39010-39017, 2019 Oct 23.
Artigo em Inglês | MEDLINE | ID: mdl-31547651

RESUMO

Herein, we investigate the role of processing solvent additives on the formation of polymer-perylene diimide bulk-heterojunction active layers for organic photovoltaics using both spin-coating and slot-die coating methods. We compare the effect of 1,8-diiodooctane (DIO) and diphenyl ether (DPE) as solvent additives on the aggregation behavior of the non-fullerene acceptor, N-annulated perylene diimide dimer (tPDI2N-EH), in neat films and blended films with the benzodithiophene-quinoxaline (BDT-QX, QX-3) donor polymer, processed from toluene in air. DIO processing crystallizes the tPDI2N-EH acceptor and leads to the decreased solar cell performance. DPE processing has a more subtle effect on the bulk-heterojunction morphology and leads to an improved solar cell performance. A comparison of the spin-coating vs slot-die coating methods shows that the effect of DPE is prominent for the slot-die coated active layers. While similar device power conversion efficiencies are achieved with active layers coated with both methods (ca. 7.3% vs 6.5%), the use of DPE improves the film quality when the slot-die coating method is employed.

5.
Chem Commun (Camb) ; 55(74): 11095-11098, 2019 Sep 21.
Artigo em Inglês | MEDLINE | ID: mdl-31460525

RESUMO

The electrophilic borylation of 2,5-diarylpyrazines results in the formation of boron-nitrogen doped dihydroindeno[1,2-b]fluorene which can be synthesized using standard Schlenk techniques and worked up and handled readily under atmospheric conditions. Through transmetallation via diarylzinc reagents a series of derivatives were synthesized which show broad visible to near-IR light absorption profiles that highlight the versatility of this BN substituted core for use in optoelectronic devices. The synthesis is efficient, scalable and allows for tuning through changes in substituents on the planar heterocyclic core and at boron. Exploratory evaluation in organic solar cell devices as non-fullerene acceptors gave power conversion efficiencies of 2%.

6.
Soft Matter ; 15(25): 5138-5146, 2019 Jun 26.
Artigo em Inglês | MEDLINE | ID: mdl-31190040

RESUMO

The controlled aggregation of organic π-conjugated molecular semiconductors within a host material (often a polymer) is important for obtaining appropriate organic film morphologies and mechanical properties for optoelectronic applications. In this study, we demonstrate how we have challenged the twisting effect in perylene diimide dimers, which is known to hinder their aggregation. Indeed, a twisted N-annulated perylene diimide dimer (tPDI2N-EH) can be induced to form crystalline aggregates within a host poly-3-hexylthiophene (P3HT) polymer matrix using solution processing. The size of the aggregates can be controlled using varying amounts of the common processing solvent additive 1,8-diiodooctane (DIO) during film formation, by changing the concentration of the molecule within the polymer film, and by adjusting the film drying time. A combination of UV-visible spectroscopy, fluorescence microscopy, cross-polarized light microscopy, and atomic force microscopy were used to characterize the organic films.

7.
Chem Rec ; 19(6): 961, 2019 06.
Artigo em Inglês | MEDLINE | ID: mdl-31136101
8.
Chem Rec ; 19(6): 989-1007, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-30511816

RESUMO

This personal account describes the pursuit of non-fullerene acceptors designed from simple and accessible organic pi-conjugated building blocks and assembled through efficient direct (hetero)arylation cross-coupling protocols. Initial materials development focused on isoindigo and diketopyrrolopyrrole organic dyes flanked by imide-based terminal acceptors. Efficiencies in solution-processed organic solar cells were modest but highlighted the potential of the material design. Materials performance was improved through structural engineering to pair perylene diimide with these organic dyes. Optimization of active layer processing and solar cell device fabrication identified the perylene diimide flanked diketopyrrolopyrrole structure as the best framework, with fullerene-free organic solar cells achieving power conversion efficiencies above 6 %. This material has met our criteria for a simple wide band gap fullerene alternative for pairing with a range of donor polymers.

9.
Chem Commun (Camb) ; 54(81): 11443-11446, 2018 Oct 09.
Artigo em Inglês | MEDLINE | ID: mdl-30250948

RESUMO

This study reports on the synthesis of an indancenodithiophene perylene diimide tetramer via unique direct (hetero)arylation reactivity. The thiophene based core structure is shown to be easily functionalized with four perylene diimides at the four active C-H positions. This new reactivity provides a simple synthetic pathway towards tetrameric perylene diimides which have emerged as one of the best classes of electron acceptors for organic solar cells.

10.
Molecules ; 23(4)2018 Apr 17.
Artigo em Inglês | MEDLINE | ID: mdl-29673207

RESUMO

Herein we report on the synthesis of an N-annulated perylene diimide (PDI) disubstituted thieno[3,4-c]pyrrole-4,6-dione (TPD) molecular acceptor (PDI-TPD-PDI) by direct heteroarylation (DHA) methods. Three sets of DHA conditions that explore the effects of solvent, temperature, and catalyst were employed to find the optimal conditions for the synthesis of two PDI-TPD-PDI derivatives. We then selected one PDI-TPD-PDI for use as a non-fullerene acceptor in organic solar cell devices with the donor polymer PBDB-T. Active layer bulk-heterojunction blends were modified using several post-deposition treatments, including thermal annealing, solvent vapour annealing, and high boiling solvent additives. It was found that active layers cast from o-dichlorobenzene with a 3% v/v diphenylether additive yielded films with adequate phase separation, and subsequently gave the best organic solar cell performance, with power conversion efficiencies greater than 3%.


Assuntos
Perileno/química , Energia Solar , Fontes de Energia Elétrica
11.
Molecules ; 23(4)2018 Apr 20.
Artigo em Inglês | MEDLINE | ID: mdl-29677127

RESUMO

The synthesis and preliminary evaluation as donor material for organic photovoltaics of the poly(diketopyrrolopyrrole-spirobifluorene) (PDPPSBF) is reported herein. Prepared via homogeneous and heterogeneous direct (hetero)arylation polymerization (DHAP), through the use of different catalytic systems, conjugated polymers with comparable molecular weights were obtained. The polymers exhibited strong optical absorption out to 700 nm as thin-films and had appropriate electronic energy levels for use as a donor with PC70BM. Bulk heterojunction solar cells were fabricated giving power conversion efficiencies above 4%. These results reveal the potential of such polymers prepared in only three steps from affordable and commercially available starting materials.


Assuntos
Fluorenos/química , Polimerização , Pirróis/química , Microscopia de Força Atômica , Estrutura Molecular , Polímeros/química , Energia Solar , Análise Espectral
12.
Chem Commun (Camb) ; 53(76): 10608, 2017 09 21.
Artigo em Inglês | MEDLINE | ID: mdl-28901352

RESUMO

Correction for 'An unsymmetrical non-fullerene acceptor: synthesis via direct heteroarylation, self-assembly, and utility as a low energy absorber in organic photovoltaic cells' by Abby-Jo Payne et al., Chem. Commun., 2017, 53, 10168-10171.

13.
Chem Commun (Camb) ; 53(73): 10168-10171, 2017 Sep 12.
Artigo em Inglês | MEDLINE | ID: mdl-28852753

RESUMO

This study reports on the design and synthesis of an unsymmetrical π-conjugated organic molecule composed of perylene diimide, thienyl diketopyrrolopyrrole, and indoloquinoxaline pieced together using direct heteroarylation. This material demonstrates unprecedented response in the thin-film upon post-deposition solvent vapor annealing, resulting in dramatic red-shifts in optical absorption. Such changes were utilized to enhance photocurrent generation in P3HT based organic solar cells.

14.
Org Biomol Chem ; 15(15): 3310-3319, 2017 Apr 11.
Artigo em Inglês | MEDLINE | ID: mdl-28361153

RESUMO

This study reports on the synthesis and characterization of four molecular π-extended squaraine compounds relevant to the field of organic electronics. The compounds each consist of a bis-indole squaraine core end-capped with indoloquinoxaline units employing three different bridging units, namely thiophene, thiazole, and acetylene. Compound 10 bears a thiophene bridge, 11 consists of a thiophene bridge and fluorinated indoloquinoxaline terminal units, and compounds 12 and 13 are bridged by thiazole and acetylene, respectively. The final compounds are constructed using the atom economical direct (hetero)arylation or the classic Sonogashira carbon-carbon bond formation protocols. Each carbon-carbon bond forming reaction employing thiophene bridges (i.e. synthesis of compounds 10 and 11) has been optimized using the stable and reusable silica supported Pd catalyst, SiliaCat® DPP-Pd, streamlining the synthetic procedure. While compounds 12 and 13 were also accessible using the SiliaCat® DPP-Pd catalyst, the use of Herrmann-Beller and Pd(PPh3)4 catalysts, respectively, lead to improved isolated yields of the final materials. Compounds 10-13 were characterized by thermal gravimetric analysis, cyclic voltammetry, optical absorption spectroscopy, photoluminescence spectroscopy, and each structure was analysed using density functional theory. All compounds exhibit high thermal stability and good solubility in common organic solvents, including in the greener alternative 2-methyl tetrahydrofuran. The reported compounds display stable ambipolar redox behaviour, furthermore, we have demonstrated that the frontier molecular energy levels can be effectively tuned by changing the bridging unit as predicted by density functional theory. Most striking is the drastic optical absorption profile changes observed from this class of materials upon post-deposition film annealing, suggesting molecular rearrangement in the solid-state. The induced changes and fine structure observed upon post-deposition annealing is unique to these π-extended squaraines with nothing like it reported in the literature for related squaraine based materials.

15.
Chem Commun (Camb) ; 53(6): 1164-1167, 2017 Jan 17.
Artigo em Inglês | MEDLINE | ID: mdl-28054077

RESUMO

Progress towards practical organic solar cells amenable to large scale production is reported. Fullerene-free organic solar cells with a PCE of ∼4.8% are achieved based upon an active layer composed of the standard donor polymer PTB7-Th and a highly soluble twisted PDI acceptor tPDI-Hex. All devices can be fabricated and tested in air with 'as-cast' active layers being processed from the greener solvents o-xylene (or trimethyl benzene) or the eco-friendly and bio-derived solvent 2Me-THF without loss in efficiency.

16.
Phys Chem Chem Phys ; 18(21): 14709-19, 2016 06 07.
Artigo em Inglês | MEDLINE | ID: mdl-27185588

RESUMO

Five organic π-conjugated small molecules with bithiophene-phthalimide backbones bearing alkyl chains of different symmetry, length and branching character were synthesized using optimized microwave and direct heteroarylation protocols. The chosen alkyl chains were 1-ethylpropyl, 1-methylbutyl, pentyl, hexyl and octyl. A sixth compound was also synthesized replacing the phthalimide terminal units with octylnaphthalimide for additional scope. Through the thorough analysis of both thermal and optical properties and the investigation of self-assembly tendencies by single crystal X-ray diffraction and variable angle spectroscopic ellipsometry it is evident that alkyl side chains and building block size influence many facets of material properties. Within this class of materials the 1-ethylpropyl derivative exhibited the most unique behaviour.

17.
Phys Chem Chem Phys ; 18(18): 12476-85, 2016 05 14.
Artigo em Inglês | MEDLINE | ID: mdl-27087259

RESUMO

Bulk-heterojunction (BHJ) molecular blends prepared from small molecules based on diketopyrrolopyrrole (DPP) and perylene-diimide (PDI) chromophores have been studied using optical absorption, cyclic voltammetry, photoluminescence quenching, X-ray diffraction, atomic force microscopy, and current-voltage measurements. The results provided useful insights into the use of DPP and PDI based molecules as donor-acceptor composites for organic photovoltaic (OPV) applications. Beside optoelectronic compatibility, the choice of active layer processing conditions is of key importance to improve the performance of BHJ solar cells. In this context, post-production treatments, viz. thermal and solvent vapour annealing, and the use of 1,8-diiodooctane as a solvent additive were employed to optimize the morphology of blend films. X-ray diffraction and atomic force microscopy indicated that the aforementioned processing strategies led to non-optimal composite morphologies with significantly large crystallites in comparison to exciton diffusion lengths. Although the open circuit voltage of the OPV devices was satisfactory (0.78 V), it was anticipated that the bulky domains hamper charge dissociation and transport, which resulted in low photovoltaic performance.

18.
Chemphyschem ; 16(6): 1190-202, 2015 Apr 27.
Artigo em Inglês | MEDLINE | ID: mdl-25418978

RESUMO

An electron-deficient small molecule accessible from sustainable isoindigo and phthalimide building blocks was synthesized via optimized synthetic procedures that incorporate microwave-assisted synthesis and a heterogeneous catalyst for Suzuki coupling, and direct heteroarylation carbon-carbon bond forming reactions. The material was designed as a non-fullerene acceptor with the help of DFT calculations and characterized by optical, electronic, and thermal analysis. Further investigation of the material revealed a differing solid-state morphology with the use of three well-known processing conditions: thermal annealing, solvent vapor annealing and small volume fractions of 1,8-diiodooctane (DIO) additive. These unique morphologies persist in the active layer blends and have demonstrated a distinct influence on device performance. Organic photovoltaic-bulk heterojunction (OPV-BHJ) devices show an inherently high open circuit voltage (Voc ) with the best power conversion efficiency (PCE) cells reaching 1.0 V with 0.4 v/v % DIO as a processing additive.

19.
J Phys Chem A ; 118(36): 7939-51, 2014 Sep 11.
Artigo em Inglês | MEDLINE | ID: mdl-25111089

RESUMO

In an effort to seek high-performance small molecule electron acceptor materials for use in heterojunction solar cells, computational chemistry was used to examine a variety of terminal acceptor-conjugated bridge-core acceptor-conjugated bridge-terminal acceptor small molecules. In particular, we have systematically predicted the geometric, electronic, and optical properties of 16 potential small-molecule acceptors based upon a series of electron deficient π-conjugated building blocks that have been incorporated into materials exhibiting good electron transport properties. Results show that the band gap, HOMO/LUMO energy levels, orbital spatial distribution, and intrinsic dipole moments can be systematically altered by varying the electron properties of the terminal or core acceptor units. In addition, the identity of the conjugated bridge can help fine-tune the electronic properties of the molecule, where this study showed that the strongest electron affinity of the conjugated π-bridge increased the stability in the HOMO and LUMO energies and increased the band gap of these small-molecule acceptors. As a result, this work points toward an isoindigo (C5) core combined with C2-thienopyrrole dione (A5) terminal units as the most promising small molecule acceptor material that can be fine-tuned with the choice of conjugated bridge and may be considered as reasonable candidates for synthesis and incorporation into organic solar cells.

20.
Acc Chem Res ; 47(1): 257-70, 2014 Jan 21.
Artigo em Inglês | MEDLINE | ID: mdl-23984626

RESUMO

Organic semiconductors incorporated into solar cells using a bulk heterojunction (BHJ) construction show promise as a cleaner answer to increasing energy needs throughout the world. Organic solar cells based on the BHJ architecture have steadily increased in their device performance over the past two decades, with power conversion efficiencies reaching 10%. Much of this success has come with conjugated polymer/fullerene combinations, where optimized polymer design strategies, synthetic protocols, device fabrication procedures, and characterization methods have provided significant advancements in the technology. More recently, chemists have been paying particular attention to well-defined molecular donor systems due to their ease of functionalization, amenability to standard organic purification and characterization methods, and reduced batch-to-batch variability compared to polymer counterparts. There are several critical properties for efficient small molecule donors. First, broad optical absorption needs to extend towards the near-IR region to achieve spectral overlap with the solar spectrum. Second, the low lying highest occupied molecular orbital (HOMO) energy levels need to be between -5.2 and -5.5 eV to ensure acceptable device open circuit voltages. Third, the structures need to be relatively planar to ensure close intermolecular contacts and high charge carrier mobilities. And last, the small molecule donors need to be sufficiently soluble in organic solvents (≥10 mg/mL) to facilitate solution deposition of thin films of appropriate uniformity and thickness. Ideally, these molecules should be constructed from cost-effective, sustainable building blocks using established, high yielding reactions in as few steps as possible. The structures should also be easy to functionalize to maximize tunability for desired properties. In this Account, we present a chronological description of our thought process and design strategies used in the development of highly efficient molecular donors that achieve power conversion efficiencies greater than 7%. The molecules are based on a modular D(1)-A-D(2)-A-D(1) architecture, where A is an asymmetric electron deficient heterocycle, which allowed us to quickly access a library of compounds and develop structure-property-performance relationships. Modifications to the D1 and D2 units enable spectral coverage throughout the entire visible region and control of HOMO energy levels, while adjustments to the pendant alkyl substituents dictate molecular solubility, thermal transition temperatures, and solid-state organizational tendencies. Additionally, we discuss regiochemical considerations that highlight how individual atom placements can significantly influence molecular and subsequently device characteristics. Our results demonstrate the utility of this architecture for generating promising materials to be integrated into organic photovoltaic devices, call attention to areas for improvement, and provide guiding principles to sustain the steady increases necessary to move this technology forward.

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