Charge Photogeneration for a Series of Thiazolo‐Thiazole Donor Polymers Blended with the Fullerene Electron Acceptors PCBM and ICBA

Shoaee, Safa; Subramaniyan, Selvam; Xin, Hao; Keiderling, Chaz; Tuladhar, Pabitra Shakya; Jamieson, Fiona C.; Jenekhe, Samson A.; Durrant, James R.

doi:10.1002/adfm.201203148

Cited by 169 publications

(217 citation statements)

References 59 publications

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“…19 Ignoring complications associated with the fact that charge transfer to the acceptor may be affected for better or worse, the mixed and pure donor phases can be considered as donor 1 and donor 2 phases, with slightly shifted energy levels due to the aggregation. From the discussion of Figures 6 and 7 it then follows that such a 3-phase morphology is sub-optimal in case of a donor with a broad absorption spectrum.…”

Section: Articlementioning

confidence: 99%

“…We shall finally draw an analogy between the present results and the 3-phase morphology encountered in binary OPV systems in which pure and aggregated donor and acceptor Please do not adjust margins Please do not adjust margins phases coexist with an amorphous mixed phase. 19 Ignoring complications associated with the fact that charge transfer to the acceptor may be affected for better or worse, the mixed and pure donor phases can be considered as donor 1 and donor 2 phases, with slightly shifted energy levels due to the aggregation. From the discussion of Figures 6 and 7 it then follows that such a 3-phase morphology is sub-optimal in case of a donor with a broad absorption spectrum.…”

Section: Selecting Optimal Donor Materials and Compositionsmentioning

confidence: 99%

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Open circuit voltage and efficiency in ternary organic photovoltaic blends

Felekidis

Wang

Kemerink

2016

Energy Environ. Sci.

104

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Organic bulk heterojunction solar cells based on ternary blends of two donor absorbers and one acceptor are investigated by experiments and modeling. The commonly observed continuous tunability of the open circuit voltage with donor1:donor2 ratio can quantitatively be explained as quasi-Fermi level splitting due to photocreated charges filling a joint density of states that is broadened by Gaussian disorder. On this basis, a predictive model for the power conversion efficiency that accounts for the composition-dependent absorption and the shape of the current-voltage characteristic is developed. When all other parameters, most notably the fill factor, are constant, we find that for state-of-the-art absorbers, having a broad and strong absorption spectrum, ternary blends offer no advantage over binary ones. For absorbers with a more narrow absorption spectrum ternary blends of donors with complementary absorption spectra, offer modest improvements over binary ones. In contrast, when, upon blending, transport and/or recombination kinetics are improved, leading to an increased fill factor, ternaries may offer significant advantages over binaries. Broader contextSolar cells based on blends of organic semiconductors almost routinely reach power conversion efficiencies (PCE) in the 10% range. One of the strategies that has been proposed to push this limit further upward is the use of so-called ternary blends in which two instead of one absorbing donor material is blended with the electron acceptor. Systematic improvement of PCE by ternary blending has been reported. Despite the experimental success, the current understanding of both the PCE enhancement and the underlying puzzling tunability of the open circuit voltage Voc is limited and essentially qualitative. In this contribution we develop and validate a quantitative and predictive framework for both the Voc and PCE of ternary organic solar cells, which allows us to propose design rules. In contrast to current wisdom, we demonstrate that PCE enhancement in ternary blends hardly results from optimizing the overlap with the solar spectrum but predominantly from synergetic improvement of the charge transport and recombination kinetics. The model can be easily extended to include more detail and will allow other researchers to upfront evaluate the photovoltaic potential of 'any' ternary material combination. 10 On the same basis Savoie et al. proposed an empirical expression for Voc as a current-weighted average of the two sub-systems and used this to estimate a maximal theoretical PCE (of 13%) for varying donor bandgaps. 11 Apart from lacking a formal basis, there are two problems with the parallel junction picture. First, it relies on a specific morphology in the active layer that allows different regions to act as independent binary cells that are electrically decoupled. Even if a fortunate morphology would lead to the presence of two (hole-) percolating networks that are electrically isolated from each other, the presence of metal contacts does unavoidably enforce...

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Section: Articlementioning

confidence: 99%

Section: Selecting Optimal Donor Materials and Compositionsmentioning

confidence: 99%

Open circuit voltage and efficiency in ternary organic photovoltaic blends

Felekidis

Wang

Kemerink

2016

Energy Environ. Sci.

104

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“…These results are in agreement with recent spectroscopic studies of polymer:fullerene systems where we fi nd that materials crystallinity does have a strong impact upon the recombination dynamics of the initially generated polarons. [ 48 ] At high energetic offsets (high Δ E LUMO ) the offset in potential energy might dominate the Gibbs free energy, making other contributions less important, but as Δ E LUMO is lowered, these material-dependent quantities will become more pronounced. Charge generation yield in various polymer-fullerene blends, measured with TAS at 300 ns (2 μ s for PCDTBT due to the fast decay component).…”

Section: Studies Of Charge Collection Effi Ciency Of the Blend Filmsmentioning

confidence: 99%

Understanding the Reduced Efficiencies of Organic Solar Cells Employing Fullerene Multiadducts as Acceptors

Faist

Shoaee

Tuladhar

et al. 2013

Advanced Energy Materials

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134

140

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The use of fullerenes with two or more adducts as acceptors has been recently shown to enhance the performance of bulk‐heterojunction solar cells using poly(3‐hexylthiophene) (P3HT) as the donor. The enhancement is caused by a substantial increase in the open‐circuit voltage due to a rise in the fullerene lowest unoccupied molecular orbital (LUMO) level when going from monoadducts to multiadducts. While the increase in the open‐circuit voltage is obtained with many different polymers, most polymers other than P3HT show a substantially reduced photocurrent when blended with fullerene multiadducts like bis‐PCBM (bis adduct of Phenyl‐C61‐butyric acid methyl ester) or the indene C60 bis‐adduct ICBA. Here we investigate the reasons for this decrease in photocurrent. We find that it can be attributed partly to a loss in charge generation efficiency that may be related to the LUMO‐LUMO and HOMO‐HOMO (highest occupied molecular orbital) offsets at the donor‐acceptor heterojunction, and partly to reduced charge carrier collection efficiencies. We show that the P3HT exhibits efficient collection due to high hole and electron mobilities with mono‐ and multiadduct fullerenes. In contrast the less crystalline polymer Poly[[9‐(1‐octylnonyl)‐9H‐carbazole‐2,7‐diyl]‐2,5‐thiophenediyl‐2,1,3‐benzothiadiazole‐4,7‐diyl‐2,5‐thiophenediyl (PCDTBT) shows inefficient charge carrier collection, assigned to low hole mobility in the polymer and low electron mobility when blended with multiadduct fullerenes.

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“…P3HT chains within the mixed domains are believed to exhibit a twisted 923 conformation, similar to chains in solution or in a solid sample of regiorandom 924 P3HT. As these twisted chains exhibit lower HOMO energies than those in crys-925 tallites of planar P3HT [176], an energy gradient is established that drives holes out 926 of the intermixed regions [177]. Similarly, Jamieson et al pointed out recently that 927 the larger electron affinity of PCBM molecules in pure fullerene aggregates com-928 pared to the intermixed domain assists free charge generation [178].…”

mentioning

confidence: 99%

“…Therefore, a morphological driving force is established that counterbalances the mutual Coulombic interaction of the geminate pair. Reprinted (adapted) with permission from [177]. Copyright © 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.…”

mentioning

confidence: 99%

P3HT-Based Solar Cells: Structural Properties and Photovoltaic Performance

Moulé

Neher

Turner

2014

P3HT Revisited – From Molecular Scale to Solar Cell Devices

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Each year we are bombarded with B.Sc. and Ph.D. applications from 8 students that want to improve the world. They have learned that their future depends 9 on changing the type of fuel we use and that solar energy is our future. The hope and 10 energy of these young people will transform future energy technologies, but it will 11 not happen quickly. Organic photovoltaic devices are easy to draw AU1, but the mate-12 rials, processing steps, and ways of measuring the properties of the materials are 13 very complicated. It is not trivial to make a systematic measurement that will 14 change the way other research groups think or practice. In approaching this chapter, 15 we thought about what a new researcher would need to know about organic 16 photovoltaic devices and materials in order to have a good start in the subject. [1][2][3][4]. Similar 43 to the gold rush in the 1800s and the oil boom in the 1900s, intellectual property on 44 new technologies is now the boom industry for innovative people to become rich 45 and influential fast. In the twenty-first century, scientists and engineers are the 46 pioneers and our ideas are the prize. One of the most alluring energy technologies of 47 the past decade has been organic photovoltaics (OPV). This technology is alluring 48 because it could potentially reduce the cost of producing photovoltaic 49 (PV) modules and thereby make solar energy cost-competitive with fossil fuels. 50 As can be seen in Fig. 1, the allure of OPV brought thousands of scientists and 51 engineers into this new field, generating an exponential increase in scientific 52 knowledge (as measured by the number of scientific AU4 articles) in this area. The 53 sharp focus on OPV technology has led to an explosion of interest in enabling 54 technologies such as polymer synthesis, polymer physics, microstructural measure-55 ment techniques, multiscale modeling, photophysics, organic electronics, organic-56 inorganic hybrid materials, etc. All of this intense focus into one research area has 57 also created intense competition between research groups. With so many new 58 scientific articles published yearly, it is impossible to read them all, and repeat or 59 redundant articles have become unfortunately and unavoidably common. Even 60 review articles and books about OPV have proliferated, making production of an 61 original perspective difficult and a complete literature review impractical. We 62 apologize in advance if any important work is not cited here. 63Under this backdrop, we have decided to produce an article that is designed to be 64 helpful to students and postdocs who are entering this field. Rather than focusing on 65 the efficiency of devices or the morphology of materials (subjects that are covered 66 very well elsewhere), we instead focus some attention on how to approach OPV 67 research from a more practical (laboratory-based) perspective. Section 1 introduces A.J. Moulé et al. 68OPV devices, modules, and scale-up. Section 2 discusses fabrication of poly-3- Device Characterist...

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Charge Photogeneration for a Series of Thiazolo‐Thiazole Donor Polymers Blended with the Fullerene Electron Acceptors PCBM and ICBA

Cited by 169 publications

References 59 publications

Open circuit voltage and efficiency in ternary organic photovoltaic blends

Open circuit voltage and efficiency in ternary organic photovoltaic blends

Understanding the Reduced Efficiencies of Organic Solar Cells Employing Fullerene Multiadducts as Acceptors

P3HT-Based Solar Cells: Structural Properties and Photovoltaic Performance

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