Formation of highly crystalline and texturized donor domains in DPP(TBFu)2:PC71BM SM-BHJ devices via solvent vapour annealing: implications for device function

Viterisi, Aurélien; Gispert-Guirado, Francesc; Ryan, James W.; Palomares, Emilio

doi:10.1039/c2jm31235b

Cited by 65 publications

(69 citation statements)

References 51 publications

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“…Note how, in the case of p-DTS(FBTTh 2 ) 2 /PC 71 BM/DIO, one observes clear attenuation of the metastable peak at 45 s. wileyonlinelibrary.com PS-containing fi lms exhibit different time-dependent behavior: in p-DTS(FBTTh 2 ) 2 /PC 71 BM/PS fi lms, the crystalline peak appears at 6 s together with the metastable peak. The (002) refl ection grows in at 5.6 nm −1 over the next 20 s, indicating long-range order, and the intensity at 4.4 nm −1 does not signifi cantly change after 45 s. Although chlorobenzene has been used in the past to increase SM crystallinity via solvent annealing, [ 20 ] the amount of retained chlorobenzene by PS-containing fi lms and the rate at which the solvent is lost appear to be insuffi cient to allow for conversion from the metastable to crystalline phases within the bulk fi lm of this BHJ system. [ 18 ] p-DTS(FBTTh 2 ) 2 /PC 71 BM/PS/ DIO fi lms exhibit a time-dependent behavior characteristic of both types of additives.…”

Section: Crystallinity Evolution Via In Situ Grazing-incidence Wide-amentioning

confidence: 98%

Synergistic Impact of Solvent and Polymer Additives on the Film Formation of Small Molecule Blend Films for Bulk Heterojunction Solar Cells

McDowell

Abdelsamie

Zhao

et al. 2015

Advanced Energy Materials

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Small molecule (SM) donors have emerged as viable alternatives to the more widely studied conjugated polymer counterparts primarily since they lack batch-to-batch variability and can be simpler to purify. [ 2,3 ] However, the lower viscosity of SM solutions can make fi lm formation from solution more challenging, particularly in terms of surface wetting and for achieving signifi cant fi lm thicknesses. [ 4 ] It has been determined empirically that nanostructures suitable optimum solar cell performance are often achieved through thermal annealing and/or high-boiling point solvent additives. [5][6][7] Neither treatment addresses the fi lm formation difficulties of SM solutions.Adding small quantities of an inert polymer can increase the fi lm thickness of molecular solar cells and transistors. [ 8 ] Specifi cally, high molecular weight polystryrene (PS) has been shown to increase solar cell power conversion efficiency (PCE) of 7,7′-(4,4-bis (FBTTh 2 ) 2 ) and [6,6]-phenyl C 71 -butyric acid methyl ester (PC 71 BM) blends from chlorobenzene. Including a high-boiling point solvent additive, such as diiodooctane (DIO), further increases effi ciency. [ 9 ] Molecular structures are shown in Figure 1 . This increased effi ciency arises from thickening the BHJ layer fi lm without impacting hole mobility, [ 10 ] which is at fi rst sight surprising given the insulating nature of PS. In this investigation, we combine a set of structural characterization tools to probe how the complex internal morphology of the PS-containing BHJ blend evolves prior to providing the fi nal organization found in devices and the degree to which PS and DIO work together to deliver fi lms with optimal performance. The goal is to draw generalities and mechanistic understanding that may be translatable to other active layer blends. Results and DiscussionThe following conditions were used in the studies: p-DTS(FBTTh 2 ) 2 /PC 71 BM (cast from only chlorobenzene), p-DTS(FBTTh 2 ) 2 /PC 71 BM/DIO (cast from chlorobenzene with 0.4% DIO by volume), p-DTS(FBTTh 2 ) 2 /PC 71 BM/PS (cast from chlorobenzene and 2.5% PS by total solid weight), and

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Section: Crystallinity Evolution Via In Situ Grazing-incidence Wide-amentioning

confidence: 98%

Synergistic Impact of Solvent and Polymer Additives on the Film Formation of Small Molecule Blend Films for Bulk Heterojunction Solar Cells

McDowell

Abdelsamie

Zhao

et al. 2015

Advanced Energy Materials

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“…While the effect of SVA on the device performance of polymer based BHJs was investigated in the late 2000s – early 2010s for a few polymer systems with limited success [15–18], the device performance of a number of small molecule based BHJs has been shown to significantly benefit from SVA. [9, 10, 19–27] Like the use of processing additives (e.g. 1,8-diiodooctane, DIO) for morphology control in polymeric semiconductors, SVA has a low-thermal budget and therefore is attractive for R2R-processing on flexible substrates with low glass transition temperatures.…”

Section: Introductionmentioning

confidence: 99%

Film morphology evolution during solvent vapor annealing of highly efficient small molecule donor/acceptor blends

Engmann

Herzing

et al. 2016

J. Mater. Chem. A

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Solution-processable small molecule photovoltaics based on the novel molecular donor, benzodithiophene terthiophene rhodanine (BTR), recently have shown maximum power conversion efficiencies above 8 % for active layer thicknesses up to 400 nm, using post process solvent vapor annealing (SVA) with tetrahydrofuran (THF). Here we report an in-situ study on the morphology evolution during SVA using the moderate solvent THF and the good solvent chloroform (CF). The combination of real-time grazing incidence X-ray diffraction (GIXD) and grazing incidence small angle X-ray scattering (GISAXS) allows us to draw a complete picture of the evolution of crystallinity and phase purity during post process annealing. We find that the relative crystallinity compared to the as-cast films is only modestly affected by SVA and solvent choice. However, both the phase purity and the characteristic domain sizes within the film vary significantly and are controlled by the solvent quality as well as exposure time. Using THF, films with high phase purity and desirable characteristic length scales of about 30 nm can be achieved, while the use of CF rapidly leads to excessive film coarsening and less preferable domain sizes on the order of 60 nm, too large for optimized charge separation.

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“…PEDOT:PSS was used as a hole-injection layer at the anode, and a vacuum-deposited molybdenum trioxide (MoO 3 ) layer was used as an electron-blocking layer at the cathode. 28 The thermal effect on the thin film absorption of DT-DPPðTVTÞ 2 does not appear to be completely similar to DPPðFTNaÞ 2 and DPP(TNa) 2 , recently reported by us. DT-DPPðTVTÞ 2 showed a broad absorption between 500 and 700 nm in dilute solution with two absorption maxima of nearly equal intensity at ca.…”

Section: Single-carrier Hole-only Devicementioning

confidence: 65%

Synthesis and photovoltaic response of a solution-processable dithienyldiketopyrrolopyrrole-based molecular semiconductor with thienylvinylthienyl endgroups

et al. 2015

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We describe the synthesis and preliminary photovoltaic performance of a solutionprocessable organic small-molecule electron donor DT-DPPðTVTÞ 2 that consists of dithienyldiketopyrrolopyrrole (DT-DPP) as the core and thienylvinylthiophene (TVT) as the endgroups. The new compound is a crystalline solid with a T m of approximately 216°C. Cyclic voltammetry indicates that DT-DPPðTVTÞ 2 exhibits two quasi-reversible one-electron oxidation waves at ca. 0.68 and 0.90 V versus an Ag∕AgCl reference electrode, respectively, leading to an estimated highest occupied molecular orbital (HOMO) level of about −5.08 eV. Introducing the branched 2-hexyldecyl side chain provides DT-DPPðTVTÞ 2 with a high solubility in chloroform up to ca. 36 mg mL −1 at room temperature. Thermal annealing increases the crystallinity of the as-cast film from chloroform solution, thereby rendering slightly red-shifted charge-transfer absorption maxima. Fitting the space-charge-limited current characteristics of the thermally annealed thin film yields an improved hole mobility of ∼2.14 × 10 −4 cm 2 V −1 s −1 at low voltages versus ∼1.46 × 10 −4 cm 2 V −1 s −1 of the as-cast film. A first characterization of the solar cell [ITO/ PEDOT: PSS∕DT-DPPðTVTÞ 2 : PC 61 BM∕Al] produces a power conversion efficiency of ∼3% with V OC ≈ 0.78 V, J SC ≈ 7.91 mA cm −2 , and FF ≈ 48.7%, under simulated AM1.5G with an illumination intensity of 100 mW cm −2 . It should be noted that the thermal effect on the thin film absorption of DT-DPPðTVTÞ 2 does not seem to be completely similar to the molecular donor DPPðTFNaÞ 2 reported earlier, which bears 6-fluoronaphthyl endgroups. Downloaded From: http://photonicsforenergy.spiedigitallibrary.org/ on 05/15/2015 Terms of Use: http://spiedl.org/terms Zhang et al.: Synthesis and photovoltaic response of a solution-processable dithienyldiketopyrrolopyrrole. Downloaded From: http://photonicsforenergy.spiedigitallibrary.org/ on 05/15/2015 Terms of Use: http://spiedl.org/terms Zhang et al.: Synthesis and photovoltaic response of a solution-processable dithienyldiketopyrrolopyrrole. Downloaded From: http://photonicsforenergy.spiedigitallibrary.org/ on 05/15/2015 Terms of Use: http://spiedl.org/terms Zhang et al.: Synthesis and photovoltaic response of a solution-processable dithienyldiketopyrrolopyrrole. Downloaded From: http://photonicsforenergy.spiedigitallibrary.org/ on 05/15/2015 Terms of Use: http://spiedl.org/terms Zhang et al.: Synthesis and photovoltaic response of a solution-processable dithienyldiketopyrrolopyrrole. Downloaded From: http://photonicsforenergy.spiedigitallibrary.org/ on 05/15/2015 Terms of Use: http://spiedl.org/terms Zhang et al.: Synthesis and photovoltaic response of a solution-processable dithienyldiketopyrrolopyrrole. Downloaded From: http://photonicsforenergy.spiedigitallibrary.org/ on 05/15/2015 Terms of Use: http://spiedl.org/terms Zhang et al.: Synthesis and photovoltaic response of a solution-processable dithienyldiketopyrrolopyrrole. Downloaded From: http://photonicsforenergy.spiedigitallibrary.org/...

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Formation of highly crystalline and texturized donor domains in DPP(TBFu)2:PC71BM SM-BHJ devices via solvent vapour annealing: implications for device function

Cited by 65 publications

References 51 publications

Synergistic Impact of Solvent and Polymer Additives on the Film Formation of Small Molecule Blend Films for Bulk Heterojunction Solar Cells

Synergistic Impact of Solvent and Polymer Additives on the Film Formation of Small Molecule Blend Films for Bulk Heterojunction Solar Cells

Film morphology evolution during solvent vapor annealing of highly efficient small molecule donor/acceptor blends

Synthesis and photovoltaic response of a solution-processable dithienyldiketopyrrolopyrrole-based molecular semiconductor with thienylvinylthienyl endgroups

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