Influence of the Ionic Functionalities of Polyfluorene Derivatives as a Cathode Interfacial Layer on Inverted Polymer Solar Cells

Kang, Rira; Oh, Seung‐Hwan; Kim, Dong‐Yu

doi:10.1021/am500708k

Cited by 74 publications

(59 citation statements)

References 37 publications

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“…We explore this hypothesis using photoemission spectroscopy, with the aim to propose a general model for energy level alignment involving CE interlayers. As the work function modification is strongly dependent on the ionic functionality, [34] we use a CE series with various ionic groups, including cationic poly( Table 1.The findings are surprisingly similar to recent results on interfaces featuring molecules with intrinsic dipoles [35] and for molecule-doped conjugated polymer/electrode interfaces. [36] In the former case, a potential step is induced from (partial) ordering of the molecular dipoles.…”

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confidence: 77%

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Regular Energetics at Conjugated Electrolyte/Electrode Modifier for Organic Electronics and their Implications on Design Rules

Bao

Liu

Wang

et al. 2015

Adv Materials Inter

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IntroductionPolymer-based electronic devices such as transistors, light emitting diodes and photovoltaic cells are considered to be an attractive technology with the potential advantages of high throughput, low manufacturing cost, light weight, and mechanical flexibility. [1][2][3] All such stacked devices contain several interfaces, e.g. electrode/organic and/or organic/organic, that significantly play a role in the device performance. Consequently much effort has been invested in tailoring electrodes using interlayers to optimize charge injection/extraction. [4][5][6][7][8][9][10][11] Recent reports have demonstrated that conjugated electrolytes (CEs) containing a -delocalized backbone and pendant ionic groups are very efficient charge injection/extraction interlayers for device operation, [12][13][14] as they can effectively tune the work function of metal electrodes. [12,15] Furthermore, the ionic groups render the CEs soluble in polar solvents, allowing the subsequent coating process of the organic layer with no damage to or intermixing with the underlying semiconducting polymer layer that typically is deposited with non-polar solvents. [16] Finally, since CEs feature -conjugated backbones they are reasonably efficient at transporting charge so that the relatively thick films obtained in printing processes could in theory be used without significant loss in device efficiency. The use of CEs for interface engineering in (printed) polymer electronics hence is very attractive and much effort consequently has been invested into understanding the mechanisms for non-conjugated and conjugated electrolyte-based work function modification resulting in several different models recently being presented. [15,[17][18][19][20][21][22][23][24] One approach sets the work function modification by the electrolyte as a pure interface effect where one of the charged species can achieve a more intimate contact with the electrode surface by e.g. being more mobile than the counter charge. [18] When the ions are located close to the interface, the Ion + and Ion -can interact with their respective induced image charge on the substrate, and since one of the ion species are more mobile, e.g. Ion + , those ions will move closer to the substrate and as a consequence form a "double dipole step" up-shifting the work function. [18] If the Ion -is more mobile, a double dipole step down-shifting the work function instead is formed. This effect only occurs at the interface and hence is film thickness independent. It also occurs independently of the substrate work function, but the size of the double dipole step is generally larger for metal electrodes than semiconductors (and ~negligible for insulator substrates).[18] For systems where both charges are equally mobile/immobile, e.g. zwitterion-based electrolytes, (partial) alignment of the ion-containing side chains through either interaction with the electrode at the interface or (bulk) realignment through an electric field will create dipole-induced potential steps. [21][22][23] Besides t...

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confidence: 77%

Section: Introductionmentioning

confidence: 99%

Regular Energetics at Conjugated Electrolyte/Electrode Modifier for Organic Electronics and their Implications on Design Rules

Bao

Liu

Wang

et al. 2015

Adv Materials Inter

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“…[4][5] Among the emerging conjugated polymers, conjugated polyelectrolytes (CPEs) consisting of conjugated main and side chains with various functional groups have been intensively investigated. 6 By virtue of their light-harvesting properties, CPEs have also been utilized as photosensitizers in solar cells [7][8] and fluorescent sensors. [9][10][11] The basis of the successful utilization of CPEs in optoelectronic applications is their semiconducting properties, including their large optical densities and high emission intensities for fluorescence resonance energy transfer.…”

Section: Introductionmentioning

confidence: 99%

Bimolecular Excited-State Electron Transfer with Surprisingly Long-Lived Radical Ions

et al. 2015

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“…Alcohol-soluble organic molecules have been also proved to be efficient cathode interlayers in invert PSCs [16,[29][30][31][32][33]. It was proposed that these hydrophilic organic interlayers can recover the lost open-circuit voltage (V oc ) and enhance the electron collection from the acceptor to ITO, because of the built-in field deriving from the interfacial dipole of the interlayer [11,34].…”

Section: Introductionmentioning

confidence: 99%

Zwitterionic ammonium and neutral amino molecules as cathode interlayer for inverted polymer solar cells

Zhang

Min

et al. 2014

Organic Electronics

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Influence of the Ionic Functionalities of Polyfluorene Derivatives as a Cathode Interfacial Layer on Inverted Polymer Solar Cells

Cited by 74 publications

References 37 publications

Regular Energetics at Conjugated Electrolyte/Electrode Modifier for Organic Electronics and their Implications on Design Rules

Regular Energetics at Conjugated Electrolyte/Electrode Modifier for Organic Electronics and their Implications on Design Rules

Bimolecular Excited-State Electron Transfer with Surprisingly Long-Lived Radical Ions

Zwitterionic ammonium and neutral amino molecules as cathode interlayer for inverted polymer solar cells

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