Electrochemical Considerations for Determining Absolute Frontier Orbital Energy Levels of Conjugated Polymers for Solar Cell Applications

Cardona, Claudia M.; Li, Wei; Kaifer, Ángel E.; Stockdale, David; Bazan, Guillermo C.

doi:10.1002/adma.201004554

Cited by 1,882 publications

(1,637 citation statements)

References 40 publications

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“…However, the use of the new IrCp*Cl(PyPyz) [TFSI], as additives for the HTM Spiro-OMeTAD, allowed us to observe a real improvement of the perovskite device. 22 thus obtaining values of 6.31 eV for the HOMO level. 17 From Fig.…”

confidence: 93%

New iridium complex as additive to the spiro-OMeTAD in perovskite solar cells with enhanced stability

Badia¹,

Mas‐Marzá²,

Sánchez³

et al. 2014

APL Materials

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A new iridium complex, IrCp*Cl(PyPyz)[TFSI], has been synthesized and used as additive for the hole transporter material, spiro-OMeTAD, in perovskite solar cells. The cells prepared with this Ir additive present higher efficiency than reference cells, and similar to cells prepared with Co additive. We have determined that the presence of metal complexes as additives decreases the recombination rate, as it has been observed by impedance spectroscopy. Very interestingly, while the efficiency after 3 months decreases by 22% and 70% for reference cell and cell with Co additive, respectively, the efficiency of devices containing the Ir additive is only decreased by a 4%.

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confidence: 93%

New iridium complex as additive to the spiro-OMeTAD in perovskite solar cells with enhanced stability

Badia¹,

Mas‐Marzá²,

Sánchez³

et al. 2014

APL Materials

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“…The inserted curve in Figure 1 shows that pDTTG-TPD possesses a reversible oxidation and an irreversible reduction. Based on the assumption that the absolute energy level of ferrocene/ferrocenium (Fc / Fc + ) is -5.1 eV to vacuum 17 , the energy levels of the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) were evaluated with the value of -5.68 eV and -3.88 eV according to their oxidation and reduction onset potentials. As a result the value of electrochemical band gap was calculated as 1.8 eV, which is in excellent agreement with that of optical band gap.…”

Section: Scheme 1 Synthetic Route To Pdttg-tpdmentioning

confidence: 99%

Fused Dithienogermolodithiophene Low Band Gap Polymers for High-Performance Organic Solar Cells without Processing Additives

et al. 2013

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ABSTRACT:We report the synthesis of a novel ladder-type fused ring donor, dithienogermolodithiophene, in which two thieno [3,2-b]thiophene units are held co-planar by a bridging dialkyl germanium. Polymerisation of this extended monomer with N-octylthienopyrrolodione by Stille polycondensation afforded a polymer, pDTTG-TPD, with an optical band gap of 1.75 eV combined with a high ionization potential. Bulk heterojunction solar cells based upon pDTTG-TPD:PC71BM blends afforded efficiencies up to 7.2% without the need for thermal annealing or processing additives.There has been significant recent progress in the development of conjugated polymers for use in organic field effect transistors and bulk heterojunction (BHJ) polymer solar cells. 1 One promising class of polymers for these applications are the so-called ladder polymers 2 , in which linked aromatic units such as thiophene or benzene are forced to be coplanar and fully conjugated by the use of bridging heteroatoms. 3 The enforced co-planarity reduces rotational disorder thereby lowering reorganization energy and potentially increasing charge carrier mobility. 4 The bridging atoms also serve as a point of attachment for the necessary solubilizing groups needed to ensure processable materials.Within the class of donor-acceptor ladder polymers, bridged bithiophenes have proven to be a particularly useful building block. For example donor-acceptor type copolymers of cyclopentadithiophene (a C bridge) with 2,1,3-benzothiadiazole have exhibited FET mobilities up to 3.3 cm 2 V -1 s -1 when substituted with long hexadecyl sidechains. 5 The incorporation of bulky 2-ethylhexyl sidechains affords a more amorphous polymer, which nevertheless showing promising BHJ efficiencies of 5.5% when processed from solutions with high boiling additives. 6 Changing the bridging heteroatom from C to Si (dithienosilole) or Ge (dithienogermole) for analogous benzothiadiazole co-polymers enhances crystallinity, leading to improved charge transport and a reduction in bimolecular recombination. 7 The improvement in crystallinity has been rationalised on the basis of the longer C-Si/Ge bond compared to the C-C bond, which alters the geometry of the fused heterocycle facilitating enhanced intramolecular interactions. 8 In addition the replacement of the C bridge with Si or Ge alters the electronic energy levels of the resultant polymers, generally resulting in a lowering of both the HOMO and LUMO. This has been rationalized by interaction σ* orbital of the silylene/germylene fragment with the π* orbital of the aromatic system. Based upon the promising performance of these bridged dithiophene monomers, we were interested to further extend the conjugation length of the monomer and improve its coplanarity by the incorporation of fused thieno[3,2-]thiophene (TT) instead of thiophene. 10 Thieno[3,2-b]thiophene has been widely utilized as a co-monomer in a variety of high performing polymers, where it has been shown to promote intrachain packing and improve charge carrier mobility. 11 In add...

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“…7 A second approach is to use easily accessible electrochemical methods. [8][9][10] These methods seek to correlate the IP, measured by means of PES, with the oxidation potential OP. Actually, linear relationships between these to magnitudes have been reported by several groups.…”

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confidence: 99%

“…Actually, linear relationships between these to magnitudes have been reported by several groups. [7][8][9][10] In cases where neither the IP nor the EA can be directly determined by photoemission techniques, cyclic-voltammetry can provide, besides the OP, the reduction potential from which, as discussed in Ref. 7, the EA can be derived through a linear relationship.…”

mentioning

confidence: 99%

Are Electron Affinity and Ionization Potential Intrinsic Parameters to Predict the Electron or Hole Acceptor Character of Amorphous Molecular Materials?

Louis¹,

San‐Fabián²,

Díaz-García³

et al. 2017

J. Phys. Chem. Lett.

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Electrochemical Considerations for Determining Absolute Frontier Orbital Energy Levels of Conjugated Polymers for Solar Cell Applications

Cited by 1,882 publications

References 40 publications

New iridium complex as additive to the spiro-OMeTAD in perovskite solar cells with enhanced stability

New iridium complex as additive to the spiro-OMeTAD in perovskite solar cells with enhanced stability

Fused Dithienogermolodithiophene Low Band Gap Polymers for High-Performance Organic Solar Cells without Processing Additives

Are Electron Affinity and Ionization Potential Intrinsic Parameters to Predict the Electron or Hole Acceptor Character of Amorphous Molecular Materials?

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