Dynamics of Additive Migration to Form Cathodic Interlayers in Organic Solar Cells

Vinokur, Jane; Obuchovsky, Stas; Deckman, Igal; Shoham, Lishai; Mates, Tom; Chabinyc, Michael L.; Frey, Gitti L.

doi:10.1021/acsami.7b06793

Cited by 10 publications

(13 citation statements)

References 43 publications

(82 reference statements)

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“…6,23,24 Time-of-flight secondary ion mass spectrometry (TOF-SIMS) and dynamic SIMS (DSIMS) provide a three-dimensional spatiallyresolved chemical profile; however, their lateral resolution is ∼ 50 nm-much larger than many morphological features-and the depth resolution from sputtering often must be correlated with a second measurement such as in-situ AFM. 6,7,15,23,35 Furthermore, because the material is sputtered, it generally creates fragments that make interpreting the resultant mass spectrum more difficult, and can have differences in sputtering efficiency for different materials. 23,37 Even with these limitations, SIMS is closest to a single measurement of chemical and morphological information that is widely used by the community, but still cannot answer many questions about system morphology because of its limited spatial resolution and fragmentation of molecular species.…”

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confidence: 99%

Atom Probe Tomography of Molecular Organic Materials: Sub-Dalton Nanometer-Scale Quantification

et al. 2019

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In this paper, we demonstrate how to apply atom probe tomography (APT) to molecular organic electronic materials. We demonstrate that APT can provide an unprecedented combination of mass resolution of < 1 Da, spatial resolution of ∼ 0.3 nm in z and ∼ 1 nm in x-y, and an analytic sensitivity of ∼ 50 ppm. We detail two systems that demonstrate the power of APT to uncover structure-property relationships in organic systems that have proven extremely difficult to probe using existing techniques: (1) a model organic photovoltaic system in which we show a chemical reaction occurs at the heterointerface; and (2) a model organic lightemitting diode system in which we show molecular segregation occurs. These examples illustrate the power of APT to enable new insights into organic molecular materials.

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confidence: 99%

Atom Probe Tomography of Molecular Organic Materials: Sub-Dalton Nanometer-Scale Quantification

et al. 2019

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“…Migration and interlayer accumulation stop once a continuous interlayer is formed at the buried interface. 22 Current density-voltage (J-V) curves of OSCs incorporating different concentrations of HEG-DT and BDMT are plotted in Figure 4a and b, respectively. The average performance parameters of these devises are listed in Tables 1 and 2.…”

Section: Resultsmentioning

confidence: 99%

“…Similar results were recently reported for self-generated PEG interlayers in P3HT:PCBM devices with Al anodes. 22 It was suggested that the PEG interlayer shifted the "effective work function" of Al tuning the energetics at the interface. Indeed, the Voc and FF increase here are in good agreement with the SECO measurements (Figure 3c and 3d) and EWF estimation above.…”

Section: Resultsmentioning

confidence: 99%

“…9 the buried organic/Al or Ag interface. [19][20][21][22] This self-generated interlayer formation process, where an additive is mixed with the active organic semiconductor solution, reduces the need for an additional processing step, and it is compatible with roll-toroll processing, and most importantly, allows tuning of an interface that is generally inaccessible. 21 The key step here is additive migration towards the organic/metal interface, driven by additive-metal interaction during electrode deposition.…”

Section: Introductionmentioning

confidence: 99%

“…23 This process depends on the strength of the interaction versus other factors, such as the size of the additive, the properties of the organic semiconductor, interactions with the bottom substrate, additive surface-energy, and others. 19,22 Because additive-metal interactions generate the interlayer, and not organic/air surface energy considerations, 24 accumulation of the additive at the organic/metal interface directly improves interfacial charge carrier transfer and hence OSC performance. 19,21 Therefore, such self-generated interlayers in organic solar cells, provide a unique platform to study the interfacial energy level alignment between an organic semiconductor and metal electrode induced by the interlayer, in correlation with OSC device performance.…”

Section: Introductionmentioning

confidence: 99%

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Correlating the effective work function at buried organic/metal interfaces with organic solar cell characteristics

et al. 2018

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Tuning Contact Resistance in Top‐Contact p‐Type and n‐Type Organic Field Effect Transistors by Self‐Generated Interlayers

Sarkar

Shamieh

Verbeek

et al. 2019

Adv Funct Materials

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(1 of 9)combined with inherent mechanical flexi bility. [1] Accordingly, extensive research efforts are invested in the development of protocols suitable for flexible device fabrication, rolltoroll processing, and printing, [2] and the design and synthesis of high performance materials, specifi cally high mobility semiconductors, [3] gate insulators, [4] and printable conductors. [5] Importantly, because charge injection, extraction, and accumulation occur at the interfaces of different materials, new solution processing methodologies that control the structure and composition of interfaces in OFETs are also essential for high performances. [6] One seminal inter facial electronic process that limits OFET performances is inefficient charge car rier injection from the source electrode to the organic semiconducting channel. Efficient injection into the organic semiconductor requires Ohmic con tacts, i.e., barrierless energy level align ment at the organic/metal interface. [6a,7] The Schottky barriers, and associated contact resistance, can be reduced by aligning either the highest occupied molecular orbital (HOMO) of a ptype organic semicon ductor or the lowest unoccupied molecular orbital (LUMO) of an ntype organic semiconductor, with the work function of the metal electrode. Therefore, tuning the work function of the metal electrode is a practical approach for optimizing charge injection/extraction and hence device performance. [8] A wellestablished strategy to tune the effective work function (EWF) at the organic/metal interface is by introducing ultrathin organic or inorganic interlayers between the metal contact and the organic semiconductor. [9] In case of organic interlayer, polar molecules are placed at the semiconductor/metal interface and modify the EWF by imposing a dipole at the interface. The energy level alignment can be controllably tuned through the chemical composition of the molecule and the direction and magnitude of the dipole. [7,10] The most common techniques of depositing organic interlayers onto substrates are thermal deposition [11] and spin coating from orthogonal solvents. [12] Another wellknown technique is to deposit selfassembled monolayers (SAM) by immersing the substrate with metal electrodes in the SAM solution prior to the semiconductor Contact resistance significantly limits the performance of organic field-effect transistors (OFETs). Positioning interlayers at the metal/organic interface can tune the effective work-function and reduce contact resistance. Myriad techniques offer interlayer processing onto the metal pads in bottom-contactOFETs. However, most methods are not suitable for deposition on organic films and incompatible with top-contact OFET architectures. Here, a simple and versatile methodology is demonstrated for interlayer processing in both p-and n-type devices that is also suitable for top-contact OFETs. In this approach, judiciously selected interlayer molecules are co-deposited as additives in the semiconducting polymer active layer. During top contact dep...

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Dynamics of Additive Migration to Form Cathodic Interlayers in Organic Solar Cells

Cited by 10 publications

References 43 publications

Atom Probe Tomography of Molecular Organic Materials: Sub-Dalton Nanometer-Scale Quantification

Atom Probe Tomography of Molecular Organic Materials: Sub-Dalton Nanometer-Scale Quantification

Correlating the effective work function at buried organic/metal interfaces with organic solar cell characteristics

Tuning Contact Resistance in Top‐Contact p‐Type and n‐Type Organic Field Effect Transistors by Self‐Generated Interlayers

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