The influence of substrate heating on morphology and layer growth in C60:ZnPc bulk heterojunction solar cells

Pfuetzner, Steffen; Mickel, C.; Jankowski, Jens; Hein, Moritz; Meiss, Jan; Schuenemann, Christoph; Elschner, Chris; Levin, A. A.; Rellinghaus, Bernd; Leo, Karl; Riede, Moritz

doi:10.1016/j.orgel.2010.12.007

Cited by 62 publications

(57 citation statements)

References 24 publications

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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: 66%

“…This impressive gain has been spurred by improvements in device architecture, [ 5 ] processing, [ 6 ] materials, [ 7 ] and theoretical understanding. [ 8 ] The role of substrate heating during [ 9 ] or post [ 6 ] BHJ deposition and its impact on PCE via changing the morphology have been studied extensively from early on, however, with mixed results, leading to a clear improvement, [ 10,11 ] no change, or even a decrease [ 12,13 ] of PCE. Possible morphological effects of temperature treatments on BHJs can be roughly divided into three aspects: relative next neighbor orientation of donor/acceptor molecules, [ 14,15 ] mid-range phase separation, [ 16 ] and ordering in pure phase-separated regions.…”

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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Section: Discussionsupporting

confidence: 66%

Section: Introductionmentioning

confidence: 99%

Why Inverted Small Molecule Solar Cells Outperform Their Noninverted Counterparts

Nanova

Scherer

Schell

et al. 2015

Adv Funct Materials

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“…[ 24 ] Furthermore, Leo et al have reported a reduction of the electron mobility by about half an order of magnitude in 1:1 donor/acceptor blend layers. [ 25 ] Therefore, we can assume that the electron mobility approaches the hole mobility in our devices. Nevertheless, the limited FF of 0.45-0.50 (Table 1 ) seems to result from a comparably low hole mobility.…”

Section: Resultsmentioning

confidence: 99%

Simple, Highly Efficient Vacuum‐Processed Bulk Heterojunction Solar Cells Based on Merocyanine Dyes

Steinmann

Kronenberg

Lenze

et al. 2011

Advanced Energy Materials

142

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In order to be competitive on the energy market, organic solar cells with higher efficiency are needed. To date, polymer solar cells have retained the lead with efficiencies of up to 8%. However, research on small molecule solar cells has been catching up throughout recent years and is showing similar efficiencies, however, only for more sophisticated multilayer device configurations. In this work, a simple, highly efficient, vacuum‐processed small molecule solar cell based on merocyanine dyes – traditional colorants that can easily be mass‐produced and purified – is presented. In the past, merocyanines have been successfully introduced in solution‐processed as well as vacuum‐processed devices, demonstrating efficiencies up to 4.9%. Here, further optimization of devices is achieved while keeping the same simple layer stack, ultimately leading to efficiencies beyond the 6% mark. In addition, physical properties such as the charge carrier transport and the cell performance under various light intensities are addressed.

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“…There are usually two possible techniques to overcome the limitation: preparing bulk heterojunction by co-evaporating two materials to form a blend film; optimizing the thickness, molecular order and the morphology of organic materials. 4,5 In order to modify the structures of bulk heterojunction, controlling the growth condition [6][7][8] or introduction of buffer layers 9,10 has been investigated. High PCEs of 5-6% for single OPV cell have been reported.…”

Section: Introductionmentioning

confidence: 99%

Structural modifications of zinc phthalocyanine thin films for organic photovoltaic applications

Zhou

Taima

Miyadera

et al. 2012

Journal of Applied Physics

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Zinc phthalocyanine (ZnPc) thin films are vacuum-evaporated on bare indium-tin-oxide (ITO) coated glass by varying substrate temperature and growth rate. The samples are characterized by atomic force microscopy, X-ray diffraction and infrared spectroscopy. The temperature does not play a clear role in the crystalline growth of ZnPc possibly due to the significant structural defects on ITO surface, while it strongly influences the surface morphology and molecular alignment. The relationships between growth characteristics and performances of photovoltaics with planar heterojunction are discussed in detail. Increasing temperature or growth rate leads to a rougher surface morphology, which enables more donor/accepter interface area for photocurrent generation. Moreover, at elevated temperature, more molecules adopt standing-up geometry, resulting in a reduction in overall efficiency. The results imply that low-temperature a) Electronic mail: zhou@se.kanazawa-u.ac.jp, b) Electronic mail: taima@se.kanazawa-u.ac.jp 2 process in order to control the molecular alignment is preferred for efficient organic photovoltaics. By simply increasing the growth rate of ZnPc up to 40 Å/s at room temperature,ZnPc/C60 planar heterojunction shows an efficiency of 1.66%, compared to 1.24% for the cell when ZnPc is prepared at 0.10 Å/s.

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The influence of substrate heating on morphology and layer growth in C60:ZnPc bulk heterojunction solar cells

Cited by 62 publications

References 24 publications

Why Inverted Small Molecule Solar Cells Outperform Their Noninverted Counterparts

Why Inverted Small Molecule Solar Cells Outperform Their Noninverted Counterparts

Simple, Highly Efficient Vacuum‐Processed Bulk Heterojunction Solar Cells Based on Merocyanine Dyes

Structural modifications of zinc phthalocyanine thin films for organic photovoltaic applications

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