Fluorinated Zinc Phthalocyanine as Donor for Efficient Vacuum‐Deposited Organic Solar Cells

Meiss, Jan; Merten, A.; Hein, Moritz; Schuenemann, Christoph; Schäfer, Stefan; Tietze, Max L.; Uhrich, Christian; Pfeiffer, Martin; Leo, Karl; Riede, Moritz

doi:10.1002/adfm.201101799

Cited by 79 publications

(56 citation statements)

References 53 publications

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“…For the ZnPc/C 60 bilayer cells, the measured V oc of 0.51 V coincides with data reported by other groups. [ 14,30 ] In case of F 4 ZnPc-based bilayer devices, V oc is improved to 0.65 V, which is similar to values of up to V oc = 0.68 V for the corresponding bulk-heterojunction OPVCs. [ 14 ] A further increase to V oc = 0.77 V was detected for F 8 ZnPc/C 60 bilayer structures, improving the open circuit voltage with respect to ZnPc/C 60 bilayer cells by 50%.…”

Section: Investigation Of the J ( V ) Characteristicssupporting

confidence: 62%

“…The choice of materials is motivated by their complementary spectral absorption in the visible, confi rmed by our optical and external quantum effi ciency (EQE) measurements, and by short circuit current densities ( j sc ) of up to 12 mA cm −2 , reported for bulk-heterojunction solar cells. [ 14 ] Moreover, in comparison to other metal phthalocyanines, the frontier orbital confi guration of ZnPc is benefi cial for the performance of bilayer cells in combination with C 60 . [ 11 ] By X-ray diffraction (XRD) we are able to evidence the impact of fl uorination on the thin fi lm morphology and to correlate the good transport properties, indicated by fi ll factors of up to 55% in case of F 4 ZnPc/ C 60 cells, with the underlying structural order.…”

Section: Introductionmentioning

confidence: 99%

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The Effect of Gradual Fluorination on the Properties of F_nZnPc Thin Films and F_nZnPc/C₆₀ Bilayer Photovoltaic Cells

Brendel

Krause

Steindamm

et al. 2015

Adv Funct Materials

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Motivated by the possibility of modifying energy levels of a molecule without substantially changing its band gap, the impact of gradual fl uorination on the optical and structural properties of zinc phthalocyanine (F n ZnPc) thin fi lms and the electronic characteristics of F n ZnPc/C 60 ( n = 0, 4, 8, 16) bilayer cells is investigated. UV-vis measurements reveal similar Q-and B-band absorption of F n ZnPc thin fi lms with n = 0, 4, 8, whereas for F 16 ZnPc a different absorption pattern is detected. A correlation between structure and electronic transport is deduced. For F 4 ZnPc/C 60 cells, the enhanced long range order supports fi ll factors of 55% and an increase of the short circuit current density by 18%, compared to ZnPc/C 60 . As a parameter being sensitive to the organic/organic interface energetics, the open circuit voltage is analyzed. An enhancement of this quantity by 27% and 50% is detected for F 4 ZnPc-and F 8 ZnPc-based devices, respectively, and is attributed to an increase of the quasi-Fermi level splitting at the donor/acceptor interface. In contrast, for F 16 ZnPc/C 60 a decrease of the open circuit voltage is observed. Complementary photoelectron spectroscopy, external quantum effi ciency, and photoluminescence measurements reveal a different working principle, which is ascribed to the particular energy level alignment at the interface of the photoactive materials.

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Section: Investigation Of the J ( V ) Characteristicssupporting

confidence: 62%

Section: Introductionmentioning

confidence: 99%

The Effect of Gradual Fluorination on the Properties of F_nZnPc Thin Films and F_nZnPc/C₆₀ Bilayer Photovoltaic Cells

Brendel

Krause

Steindamm

et al. 2015

Adv Funct Materials

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“…[ 18,19 ] Due to the independence of exciton dissociation on applied voltage, the fi ll factor of solar cells with crystalline C 60 domains is expected to increase. [ 31 ] Such an increase in FF was indeed observed for inverted devices where the blend is deposited on a pristine C 60 layer, [ 11,22,32 ] whereas in this work and several others [ 12,13,23 ] no improvement for noninverted devices was achieved. We conclude that substrate heating is a necessary but not suffi cient prerequisite for an optimal BHJ composition.…”

Section: Discussionsupporting

confidence: 57%

“…[ 6,9,26 ] The equal performance of the devices is surprising given the completely distinct morphology of the active layer determined from the TEM measurements (see Figure 2). In contrast, Meiss et al [ 22 ] showed that substrate heating to 100 °C during BHJ deposition leads to a clear improvement of PCE by almost 30% for inverted cells with the same BHJ composition (3.6% for the RT and 4.6% for the heated device). We note that the higher total effi ciencies reported by Meiss et al are partially due to the doped transport layers employed in their inverted devices.…”

Section: Wileyonlinelibrarycommentioning

confidence: 87%

“…The C 60 crystallinity strongly depends on device architecture, namely if the BHJ is evaporated on a pristine C 60 layer, as in an inverted architecture, or on a pristine absorber layer as in a noninverted architecture. Based on our fi ndings from transmission electron microscopy (TEM), device characterization, and IR spectroscopy studies on the exemplary donor/acceptor system F 4 ZnPc/C 60 (see Figure 1 a) and a comparison with literature data, [ 22 ] we can state that i) for noninverted solar cells heating during deposition has a strong effect on phase separation in the BHJ but not on PCE, whereas ii) in inverted cells heating has a strong effect on phase separation and PCE via a substrate-induced local fullerene ordering and hence improved free charge generation. Our fi ndings elucidate why record effi ciencies for vacuum-deposited cells are typically achieved in inverted architecture and have important implications for future development.…”

Section: Introductionmentioning

confidence: 99%

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Why Inverted Small Molecule Solar Cells Outperform Their Noninverted Counterparts

Nanova

Scherer

Schell

et al. 2015

Adv Funct Materials

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It is shown that the effect of substrate heating on the photo conversion effi ciency in vacuum-deposited small molecule organic solar cells is closely related to the improved free charge generation in ordered C 60 regions. The formation of these ordered regions strongly depends on the deposition sequence in the device and differs therefore between inverted and noninverted cells. Substrate-induced local fullerene ordering is found in small molecule:C 60 bulk heterojunctions (BHJs) deposited on pristine C 60 at elevated temperatures. This does not occur for BHJs deposited under identical conditions on pristine donor molecule layers, despite similar degrees of phase separation in both cases. These fi ndings point to a hitherto unidentifi ed advantage of inverted over noninverted solar cells that manifests itself in a higher charge separation effi ciency.

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Doping of Organic Semiconductors

Lüssem

Riede

Leo

2012

Physics of Organic Semiconductors

Self Cite

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Björn Lü ssem studied electrical engineering at the Rheinisch-Westfälische Technische Hochschule (RWTH) in Aachen and the University of Bath and obtained his degree as Diplomingenieur in 2003. He prepared his PhD thesis at the Research Center in Jülich, Germany, in the field of molecular electronics. His thesis concentrates on scanning tunneling microscopy of pure and mixed selfassembled monolayers and has been awarded the VDE-Promotionspreis and the Günther-Leibfried-Preis. After staying at the Materials Science Laboratory of Sony in Stuttgart from 2006 to 2008, he joined Prof. Leo's group at the Technische Universität Dresden where he is now the head of the New Devices Group. His main interests are new semiconducting devices based on organic materials and their differences or similarities to inorganic semiconductors. Moritz Riede studied physics at the University of Cambridge, UK, where he received his MSc degree in 2002. He obtained his PhD degree from the University of Konstanz in 2006 for research carried out at the Fraunhofer-Institut für Solare Energiesysteme and the Freiburger Materialforschungszentrum FMF. The focus of his thesis was on solution-processed organic solar cells. After his PhD he joined the research group of Prof. Leo at the Institut für Angewandte Photophysik (IAPP) of the Technische Universität Dresden in 2007, where he is now head of the Organic Solar Cell Group. His research concentrates on small-molecule-based organic solar cells, their fundamental working principles, and strategies for device optimization. Karl Leo obtained the Diplomphysiker degree from the University of Freiburg in 1985, working with Adolf Goetzberger at the Fraunhofer-Institut für Solare Energiesysteme. In 1988, he obtained the PhD degree from the University of Stuttgart for a PhD thesis performed at the Max-Planck-Institut für Festkörperforschung in Stuttgart under the supervision of Hans Queisser. From 1989 to 1991, he was a postdoctoral researcher at AT&T Bell Laboratories in Holmdel, NJ, USA. From 1991 to 1993, he was with the Rheinisch-Westfälische Technische Hochschule (RWTH) in Aachen, Germany. Since 1993, he has been full professor of optoelectronics at the Technische Universität Dresden. Since 2002, he is also with the Fraunhofer society, currently as director of Fraunhofer COMEDD. His main current interests are novel semiconductor systems such as semiconducting organic thin films, with special emphasis to understand growth, basic device principles, and the optical response. Recently, he has also worked on device development, such as highly efficient organic LED and solar cells. His work was recognized by several awards, including the Leibniz-Award in 2002. He was involved in the founding of several companies such as Novaled AG and Heliatek GmbH. Figure 1 Operation principles of an OLED (left) and an OSC (right). Two-layer devices are shown. Reprinted with permission from Walzer et al., Chem. Rev. 107, 1233 (2007).

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Fluorinated Zinc Phthalocyanine as Donor for Efficient Vacuum‐Deposited Organic Solar Cells

Cited by 79 publications

References 53 publications

The Effect of Gradual Fluorination on the Properties of F_nZnPc Thin Films and F_nZnPc/C₆₀ Bilayer Photovoltaic Cells

The Effect of Gradual Fluorination on the Properties of F_nZnPc Thin Films and F_nZnPc/C₆₀ Bilayer Photovoltaic Cells

Why Inverted Small Molecule Solar Cells Outperform Their Noninverted Counterparts

Doping of Organic Semiconductors

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Fluorinated Zinc Phthalocyanine as Donor for Efficient Vacuum‐Deposited Organic Solar Cells

Cited by 79 publications

References 53 publications

The Effect of Gradual Fluorination on the Properties of FnZnPc Thin Films and FnZnPc/C60 Bilayer Photovoltaic Cells

The Effect of Gradual Fluorination on the Properties of FnZnPc Thin Films and FnZnPc/C60 Bilayer Photovoltaic Cells

Why Inverted Small Molecule Solar Cells Outperform Their Noninverted Counterparts

Doping of Organic Semiconductors

Contact Info

Product

Resources

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The Effect of Gradual Fluorination on the Properties of F_nZnPc Thin Films and F_nZnPc/C₆₀ Bilayer Photovoltaic Cells

The Effect of Gradual Fluorination on the Properties of F_nZnPc Thin Films and F_nZnPc/C₆₀ Bilayer Photovoltaic Cells