Ultrafast spectroscopy on water-processable PCBM: rod–coil block copolymer nanoparticles

Ganzer, Lucia; Zappia, Stefania; Russo, Mattia; Ferretti, Anna M.; Vohra, Varun; Diterlizzi, Marianna; Antognazza, Maria Rosa; Destri, Silvia; Virgili, Tersilla

doi:10.1039/d0cp05478j

Cited by 3 publications

(7 citation statements)

References 41 publications

(64 reference statements)

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“…In order to confirm these remarks, Figure 6 shows the pump probe spectra of the spin-coated BCP5 bWPNP sample annealed at 90 °C for 20 min at 0.5 and 55 ps probe delays. As reported in [ 44 ] for the other blends, the spectra are dominated by a photoinduced absorption band at 550 nm and two positive bands at around 680 nm and 470 nm. The photoinduced spectral bands have been attributed to the PCPDTBT excitons: a photoinduced absorption band related to singlet–singlet absorption and two positive ground state bleaching (GSB) bands.…”

Section: Resultssupporting

confidence: 71%

“…The pump–probe spectra of the spin-coated BCP2, BCP15, and BCP100 bWPNPs, respectively, have been previously reported [ 44 ]. A clear correlation has been highlighted between the formation of free charge generation at donor/acceptor interfaces and the length and nature of the coil blocks.…”

Section: Resultsmentioning

confidence: 99%

“…The photoinduced spectral bands have been attributed to the PCPDTBT excitons: a photoinduced absorption band related to singlet–singlet absorption and two positive ground state bleaching (GSB) bands. We see the formation of a photoinduced absorption band at around 650 nm assigned to the electron transfer from PCPDTBT moieties to PCBM [ 44 , 55 ]. This is clear evidence that the short coil length (five repeating units) allows for an efficient charge transfer in the donor/acceptor interface without the deleterious formation of the charge transfer state [ 44 ].…”

Section: Resultsmentioning

confidence: 99%

“…We see the formation of a photoinduced absorption band at around 650 nm assigned to the electron transfer from PCPDTBT moieties to PCBM [ 44 , 55 ]. This is clear evidence that the short coil length (five repeating units) allows for an efficient charge transfer in the donor/acceptor interface without the deleterious formation of the charge transfer state [ 44 ]. The photophysical characterization confirmed a similar charge transfer efficiency between the BPC2 bWPNPs and the BPC5 bWPNPs.…”

Section: Resultsmentioning

confidence: 99%

“…In particular, we studied the bWPNP morphology by means of atomic force microscopy (AFM), transmission electron microscopy (TEM), and energy filtered TEM (EFTEM), to clarify how the morphology of the nanodomains is related to the features of the different coil molecular structures in the BCPs, and how they led to different device performances. An ultrafast spectroscopy study elucidated the charge separation dynamics in the film obtained from bWPNPs [ 44 ].…”

Section: Introductionmentioning

confidence: 99%

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Rod–Coil Block Copolymer: Fullerene Blend Water-Processable Nanoparticles: How Molecular Structure Addresses Morphology and Efficiency in NP-OPVs

Ferretti¹,

Diterlizzi²,

Porzio³

et al. 2021

Nanomaterials

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The use of water-processable nanoparticles (WPNPs) is an emerging strategy for the processing of organic semiconducting materials into aqueous medium, dramatically reducing the use of chlorinated solvents and enabling the control of the nanomorphology in OPV active layers. We studied amphiphilic rod-coil block copolymers (BCPs) with a different chemical structure and length of the hydrophilic coil blocks. Using the BCPs blended with a fullerene acceptor material, we fabricated NP-OPV devices with a sustainable approach. The goal of this work is to clarify how the morphology of the nanodomains of the two active materials is addressed by the hydrophilic coil molecular structures, and in turn how the design of the materials affects the device performances. Exploiting a peculiar application of TEM, EFTEM microscopy on WPNPs, with the contribution of AFM and spectroscopic techniques, we correlate the coil structure with the device performances, demonstrating the pivotal influence of the chemical design over material properties. BCP5, bearing a coil block of five repeating units of 4-vinilpyridine (4VP), leads to working devices with efficiency comparable to the solution-processed ones for the multiple PCBM-rich cores morphology displayed by the blend WPNPs. Otherwise, BCP2 and BCP15, with 2 and 15 repeating units of 4VP, respectively, show a single large PCBM-rich core; the insertion of styrene units into the coil block of BCP100 is detrimental for the device efficiency, even if it produces an intermixed structure.

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Section: Resultssupporting

confidence: 71%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Rod–Coil Block Copolymer: Fullerene Blend Water-Processable Nanoparticles: How Molecular Structure Addresses Morphology and Efficiency in NP-OPVs

Ferretti¹,

Diterlizzi²,

Porzio³

et al. 2021

Nanomaterials

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Optical Gain in Semiconducting Polymer Nano and Mesoparticles

Geoghegan

Mróz

Botta³

et al. 2021

Molecules

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The presence of excited-states and charge-separated species was identified through UV and visible laser pump and visible/near-infrared probe femtosecond transient absorption spectroscopy in spin coated films of poly[N-9”-heptadecanyl-2,7-carbazole-alt-5,5-(4,7-di-2-thienyl-2′,1′,3′-benzothiadiazole)] (PCDTBT) nanoparticles and mesoparticles. Optical gain in the mesoparticle films is observed after excitation at both 400 and 610 nm. In the mesoparticle film, charge generation after UV excitation appears after around 50 ps, but little is observed after visible pump excitation. In the nanoparticle film, as for a uniform film of the pure polymer, charge formation was efficiently induced by UV excitation pump, while excitation of the low energetic absorption states (at 610 nm) induces in the nanoparticle film a large optical gain region reducing the charge formation efficiency. It is proposed that the different intermolecular interactions and molecular order within the nanoparticles and mesoparticles are responsible for their markedly different photophysical behavior. These results therefore demonstrate the possibility of a hitherto unexplored route to stimulated emission in a conjugated polymer that has relatively undemanding film preparation requirements.

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Amphiphilic PTB7-Based Rod-Coil Block Copolymer for Water-Processable Nanoparticles as an Active Layer for Sustainable Organic Photovoltaic: A Case Study

Diterlizzi

Ferretti²,

Scavia³

et al. 2022

Polymers

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We synthetized a new rod-coil block copolymer (BCP) based on the semiconducting polymerpoly({4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl}{3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl}) (PTB7) and poly-4-vinylpyridine (P4VP), tailored to produce water-processable nanoparticles (WPNPs) in blend with phenyl-C71-butyric acid methyl ester (PC71BM). The copolymer PTB7-b-P4VP was completely characterized by means of two-dimensional nuclear magnetic resonance (2D-NMR), matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF) mass spectrometry (MS), size-exclusion chromatography (SEC), and differential scanning calorimetry (DSC) to confirm the molecular structure. The WPNPs were prepared through an adapted miniemulsion approach without any surfactants. Transmission electron microscopy (TEM) images reveal the nano-segregation of two active materials inside the WPNPs. The nanostructures appear spherical with a Janus-like inner morphology. PTB7 segregated to one side of the nanoparticle, while PC71BM segregated to the other side. This morphology was consistent with the value of the surface energy obtained for the two active materials PTB7-b-P4VP and PC71BM. The WPNPs obtained were deposited as an active layer of organic solar cells (OSCs). The films obtained were characterized by UV-Visible Spectroscopy (UV-vis), atomic force microscopy (AFM), and grazing incidence X-ray diffraction (GIXRD). J-V characteristics of the WPNP-based devices were measured by obtaining a power conversion efficiency of 0.85%. Noticeably, the efficiency of the WPNP-based devices was higher than that achieved for the devices fabricated with the PTB7-based BCP dissolved in chlorinated organic solvent.

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Ultrafast spectroscopy on water-processable PCBM: rod–coil block copolymer nanoparticles

Abstract: Using ultrafast spectroscopy, we investigate the photophysics of water-processable nanoparticles composed of a block copolymer electron donor and a fullerene derivative electron acceptor.

Cited by 3 publications

References 41 publications

Rod–Coil Block Copolymer: Fullerene Blend Water-Processable Nanoparticles: How Molecular Structure Addresses Morphology and Efficiency in NP-OPVs

Rod–Coil Block Copolymer: Fullerene Blend Water-Processable Nanoparticles: How Molecular Structure Addresses Morphology and Efficiency in NP-OPVs

Optical Gain in Semiconducting Polymer Nano and Mesoparticles

Amphiphilic PTB7-Based Rod-Coil Block Copolymer for Water-Processable Nanoparticles as an Active Layer for Sustainable Organic Photovoltaic: A Case Study

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