High-Efficiency Polymer Solar Cells via the Incorporation of an Amino-Functionalized Conjugated Metallopolymer as a Cathode Interlayer

Liu, Shengjian; Zhang, Kai; Lu, Junming; Zhang, Jie; Yip, Hin‐Lap; Huang, Fei; Cao, Yong

doi:10.1021/ja408363c

Cited by 330 publications

(298 citation statements)

References 47 publications

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“…[13][14][15][16][17]28 ] Increasing, [ 15 ] constant, [ 13,16 ] and decreasing [ 17 ] work function shifts have all been reported. Part of these works comprises the characterization of complete devices, which complicates the interpretation as charge transport is involved as well.…”

Section: Work Function Reduction By Pfnmentioning

confidence: 99%

“…Important for determining the origin of the effect is also the thickness dependence of the amine-containing layer. [13][14][15][16][17] In this respect different observations have been made. Xia et al [ 15 ] reported an optimum of the work function modifi cation at 8 nm thickness and above, while Zhou et al [ 13 ] and Zhang et al [ 16 ] did not observe any thickness dependence.…”

Section: Introductionmentioning

confidence: 99%

“…[13][14][15][16][17] In this respect different observations have been made. Xia et al [ 15 ] reported an optimum of the work function modifi cation at 8 nm thickness and above, while Zhou et al [ 13 ] and Zhang et al [ 16 ] did not observe any thickness dependence. Kim et al [ 17 ] reported a thickness dependence where thicker fi lms resulted in a reduced work function modifi cation.…”

Section: Introductionmentioning

confidence: 99%

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Origin of Work Function Modification by Ionic and Amine‐Based Interface Layers

Reenen

Kouijzer

Janssen

et al. 2014

Adv Materials Inter

131

138

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can evolve into a successful thin fi lm photovoltaic technology. To this end, further improvements in the sunlight-toelectricity conversion effi ciency are still needed. To do so, not only the optoelectronic, active layer should be considered, but also the connection between this layer and the electrodes. This connection is facilitated by so-called work function modifi cation layers (WMLs) that serve to align the transport levels in the organic semiconductor and the conductor by modifi cation of the work function. Materials that are often used are poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS) for improving hole collection and injection in combination with an indium tin oxide (ITO) electrode and LiF for the electron contact in combination with an Al metal electrode. A new generation of WMLs fi rst introduced by Cao et al. is based on polyelectrolytes or tertiary aliphatic amines, such as poly [(9,9-bis(3′-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt -2,7-(9,9-dioctylfluorene)] (PFN) and the corresponding ethyl ammonium bromide. [ 1 ] Although these materials improve carrier injection or extraction in different organic diode devices, [1][2][3][4][5][6][7] the mechanism behind this improvement is not completely clear. This ambiguity hinders design, selection and optimization of new WMLs.Mechanisms that are generally considered to result in electric fi elds and concomitant work function shifts at metal-organic interfaces are doping, charge transfer, and dipole formation. [8][9][10] Regarding the work function modifi cation of amine side-groups, Lindell et al. [ 11 ] found by photoelectron spectroscopy and density functional calculations that the electron donor para-phenylenediamine chemisorbs onto atomically clean Ni in vacuum. [ 12 ] Due to partial electron transfer from the amine unit, a work function reduction of 1.55 eV is achieved, resulting in a less deep Fermi level. This explanation is not likely to hold for the technologically more relevant procedure on which we shall focus, being the deposition of WMLs from solution on a metal at atmospheric pressure: the metal is not atomically clean, which likely inhibits chemisorption. In other work by Zhou et al. [ 13 ] it is shown that the work function reduction, at atmospheric pressure, by the amine groups in poly(ethylenimine ethoxylated) (PEIE), is generally the same on different conductors. Work function modifi cation by polyelectrolytes and tertiary aliphatic amines is found to be due to the formation of a net dipole at the electrode interface, induced by interaction with its own image dipole in the electrode. In polyelectrolytes differences in size and side groups between the moving ions lead to differences in approach distance towards the surface. These differences determine magnitude and direction of the resulting dipole. In tertiary aliphatic amines the lone pairs of electrons are anticipated to shift towards their image when close to the interface rather than the nitrogen nuclei, which are sterically hindered by the alkyl side chains. ...

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Section: Work Function Reduction By Pfnmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Origin of Work Function Modification by Ionic and Amine‐Based Interface Layers

Reenen

Kouijzer

Janssen

et al. 2014

Adv Materials Inter

131

138

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“…21 Although high efficiency could be achieved with these ultra-thin films, it is still difficult to ensure the device performance reproducibility, especially for large area manufacturing. 22 Moreover, conjugated polymers face the great challenge of batch to batch variations in terms of molecular weight and polydispersity, which may have a significant influence on preparation conditions, such as thickness, solubility, and film morphology. 23 Fullerene derivatives functionalized with polar pendents are emerging as novel EC interfacial materials to facilitate electron extraction in OSCs due to the circumvention of the undesirable effects often associated with previous reported interlayers.…”

Section: Introductionmentioning

confidence: 99%

High Efficiency Inverted Organic Solar Cells with a Neutral Fulleropyrrolidine Electron-Collecting Interlayer

Yan

Kan

et al. 2016

ACS Appl. Mater. Interfaces

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A novel fulleropyrrolidine derivative, named as FPNOH, was designed, synthesized and utilized as an efficient electron-collecting (EC) layer for inverted organic solar cells (i-OSCs). The grafted diethanolamino-polar moieties can not only trigger its function as an EC interlayer, but also induce orthogonal solubility that guarantees subsequent multi-layer processing without interfacial mixing. A higher power conversion efficiency (PCE) value of 8.34% was achieved for i-OSC devices with ITO/FPNOH EC electrode, compared to that of the sol-gel ZnO based reference devices with an optimized PCE value of 7.92%. High efficiency exceeding 7.7% was still achieved even for the devices with a relatively thick PFNOH film (16.9 nm). It is worthwhile to mention that this kind of material exhibits less thickness dependent performance, in contrast to widely utilized p-type conjugated polyelectrolytes (CPEs) as well as the non-conjugated polyelectrolytes (NCPEs). Further investigation on illuminating intensity dependent parameters revealed the role of FPNOH in reducing interfacial traps-induced recombination at ITO/active layer interface.

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“…Power conversion efficiency (PCE) which is higher than 9% has been reached recently [2][3][4][5][6][7][8][9][10][11][12][13][14]. Currently, BHJ OSCs are based on two types of donor materials, conjugated polymers and small molecules [15,16].…”

Section: Introductionmentioning

confidence: 99%

Synthesis and photovoltaic properties of new small molecules with rhodanine derivative as the end-capped blocks

Zhou

Xiao

Liu

et al. 2015

Organic Electronics

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a b s t r a c tTwo new acceptor-donor-acceptor (A-D-A) type small molecules DCAO3TIDT and DCNR3TIDT, with 4,4,9,9-tetrakis(4-(dodecyloxy)phenyl)-4,9-dihydro-s-indaceno-[1,2-b:5,6-b 0 ]dithiophene (IDT) as the core group and 2-ethylhexyl cyanoacetate (CAO) and 2-(1,1-dicyanomethylene)-3-octyl rhodanine (CNR) as different end-capped blocks, have been designed and synthesized. Both of them have been employed as donor for solutionprocessed bulk hetero-junction (BHJ) organic solar cells (OSCs). The two compounds showed deep highest occupied molecular orbital (HOMO) energy levels ($À5.30 eV) and strong absorption. The DCAO3TIDT and DCNR3TIDT with PC 71 BM as acceptor based BHJ solar cell devices showed short circuit current density (J sc ) of 6.93 mA/cm 2 and 8.59 mA/ cm 2 , power conversion efficiency (PCE) of 3.34% and 4.27%, respectively, and with almost same open-circuit voltage ($0.93 V), under the illumination of AM 1.5 G, 100 mW/cm 2 . The high J sc for DCNR3TIDT could result from its wider and red-shifted absorption than that of DCAO3TIDT, which was probably induced by the end-capped block rhodanine derivative. The results demonstrate that the end group would be taken into full account when designing new solution-processed small molecules, which is an important factor to determine their photovoltaic properties.

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High-Efficiency Polymer Solar Cells via the Incorporation of an Amino-Functionalized Conjugated Metallopolymer as a Cathode Interlayer

Cited by 330 publications

References 47 publications

Origin of Work Function Modification by Ionic and Amine‐Based Interface Layers

Origin of Work Function Modification by Ionic and Amine‐Based Interface Layers

High Efficiency Inverted Organic Solar Cells with a Neutral Fulleropyrrolidine Electron-Collecting Interlayer

Synthesis and photovoltaic properties of new small molecules with rhodanine derivative as the end-capped blocks

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