The Impact of Molecular Orientation on the Photovoltaic Properties of a Phthalocyanine/Fullerene Heterojunction

Rand, Barry P.; Cheyns, David; Vasseur, Karolien; Giebink, Noel C.; Mothy, Sébastien; Yi, Yuanping; Coropceanu, Veaceslav; Beljonne, David; Cornil, Jérôme; Brédas, Jean Luc; Genoe, Jan

doi:10.1002/adfm.201200512

Cited by 305 publications

(327 citation statements)

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“…For both device architectures, CT-states at the DA-interface formed upon successful exciton diffusion are inefficiently harvested as extracted photo-current. This can be attributed to incomplete CT dissociation and has been observed in ZnPc-C60-cells before by Rand et al [23] The authors attributed this finding to an unfavourable orientation of the ZnPc molecules with regard to the interface with C60. Beyond, the measurements recorded in such an exciton diffusion study can be used to evaluate the potential of a corresponding blended absorber system as discussed in SI.8.…”

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confidence: 70%

Exciton Diffusion Length and Charge Extraction Yield in Organic Bilayer Solar Cells

et al. 2017

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A method for resolving the diffusion length of excitons and the extraction yield of charge carriers is presented based on the performance of organic bilayer solar cells and careful modeling. The technique uses a simultaneous variation of the absorber thickness and the excitation wavelength. Rigorously differing solar cell structures as well as independent photoluminescence quenching measurements give consistent results.

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confidence: 70%

Exciton Diffusion Length and Charge Extraction Yield in Organic Bilayer Solar Cells

et al. 2017

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“…The stable cubic structure makes it easy to synthesize CuI thin films near room temperature using a number of chemical and physical methods, including vapor iodization (20), thermal evaporation (27), pulsed laser deposition (PLD) (28), and sputtering (29)(30)(31). Therefore, CuI is readily compatible in organic electronics, for example as (part of) the electrode in organic light-emitting diodes and organic solar cells (32)(33)(34). Recent work on the roomtemperature heteroepitaxy of CuI demonstrates its compatibility…”

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confidence: 99%

Room-temperature synthesized copper iodide thin film as degenerate p-type transparent conductor with a boosted figure of merit

Yang

Kneiβ

Lorenz

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

213

234

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A degenerate p-type conduction of cuprous iodide (CuI) thin films is achieved at the iodine-rich growth condition, allowing for the record high room-temperature conductivity of ∼156 S/cm for asdeposited CuI and ∼283 S/cm for I-doped CuI. At the same time, the films appear clear and exhibit a high transmission of 60-85% in the visible spectral range. The realization of such simultaneously high conductivity and transparency boosts the figure of merit of a p-type TC: its value jumps from ∼200 to ∼17,000 MΩ −1 . Polycrystalline CuI thin films were deposited at room temperature by reactive sputtering. Their electrical and optical properties are examined relative to other p-type transparent conductors. The transport properties of CuI thin films were investigated by temperature-dependent conductivity measurements, which reveal a semiconductor-metal transition depending on the iodine/argon ratio in the sputtering gas.copper iodide thin film | p-type transparent conductor | figure of merit | reactive sputtering | room-temperature growth

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“…[34] Similar observations have been reported by other groups as well. [35] However, as demonstrated in these publications, care has to be taken to disentangle the effect of orientation dependent ionization energies and electron affinities on the one hand, and the actual differences in electronic couplings on the other hand. [17] Moreover, the importance of long-range electrostatic interactions should not be underestimated as well.…”

Section: Reducing the Ct Strengthmentioning

confidence: 99%

Energy Losses in Small‐Molecule Organic Photovoltaics

Linderl

Zechel

Brendel

et al. 2017

Advanced Energy Materials

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processible PV technology has recently appeared as well. [5] Comparing the different technologies in terms of PCE, which is specified as the product of the short-circuit current density j SC , the open-circuit voltage V OC and the fill factor FF divided by the incoming light intensity under standard AM 1.5G illumination conditions, OPVs can well compete with their inorganic counterparts in terms of j SC or, more precisely, the external quantum efficiency and also with minor trade-off in FF, but clearly suffer from lower V OC at a given energy gap E g of the light absorbing material. While this socalled bandgap-voltage offset can be as low as 0.3-0.4 eV in Si and GaAs [6] and only a little larger in perovskite cells, [7] OPV cells exhibit energy losses of at least 0.6 eV -in many cases, however, this offset can approach and even exceed 1 eV. [8] This is currently one of the main bottlenecks toward making OPVs competitive with inorganic PV cells.In this research news, we provide the required background information on the appearance of energy losses in OPV cells, by which we mean the difference between the equivalent of the optical gap and the measured open-circuit voltage that is frequently also denoted as voltage loss, and discuss recent progress toward better understanding their origin and strategies to reduce them. To keep focused, we will mainly address small molecules as active organic semiconductors, which are being processed into thin films by vacuum deposition techniques. Compared to frequently studied π-conjugated polymers, the synthesis of small molecules is more reproducible. Moreover, a rigorous purification of small molecules is easier, which gives the opportunity to reproducibly investigate well-defined systems. The application of vacuum deposition techniques prevents the use of solvents, which as a third component in wet chemical processing can strongly influence the morphology. [9] Thus, active layers of small molecules prepared by vacuum deposition methods mark a well-controlled model system for fundamental studies such as the origin of energy losses in OPV devices. However, we expect that most of the findings can be transferred to solution-processed OPVs as well, which have considerably higher complexity in terms of local morphology and phase behavior. Excitonic Organic Solar CellsIn order to properly address energy losses in OPVs it is useful to look at their working principles in more detail (see also [10] ).

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The Impact of Molecular Orientation on the Photovoltaic Properties of a Phthalocyanine/Fullerene Heterojunction

Cited by 305 publications

References 50 publications

Exciton Diffusion Length and Charge Extraction Yield in Organic Bilayer Solar Cells

Exciton Diffusion Length and Charge Extraction Yield in Organic Bilayer Solar Cells

Room-temperature synthesized copper iodide thin film as degenerate p-type transparent conductor with a boosted figure of merit

Energy Losses in Small‐Molecule Organic Photovoltaics

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