Increase in internal quantum efficiency in small molecular oligothiophene: C60 mixed heterojunction solar cells by substrate heating

Wynands, David; Levichkova, Marieta; Leo, Karl; Uhrich, Christian; Schwartz, Gregor; Hildebrandt, Dirk; Pfeiffer, Martin; Riede, Moritz

doi:10.1063/1.3475766

Cited by 62 publications

(54 citation statements)

References 11 publications

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“…[ 28 ] In pristine layers, this oligothiophene derivative has its main absorption in the green part of the sun spectrum. It was found to have an absorption coeffi cient of (3.2 ± 0.3) × 10 5 cm − 1 at 594 nm, an ionization potential (IP) of about 5.5 eV and an optical gap of (1.70 ± 0.02)eV.…”

Section: Comparison Of Single and Tandem Devicesmentioning

confidence: 99%

“…[ 17 ] The corresponding currentvoltage ( IV ) curves under illumination are shown in Figure 3 and summarized in Table 1 . Further details on properties, performance and optimization procedures of DCV6T for single heterojunction solar cells have been previously published; [ 28 ] for F4-ZnPc they will be published elsewhere.…”

Section: Comparison Of Single and Tandem Devicesmentioning

confidence: 99%

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Efficient Organic Tandem Solar Cells based on Small Molecules

Riede

Uhrich

Widmer

et al. 2011

Adv Funct Materials

227

144

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In this paper, two vacuum processed single heterojunction organic solar cells with complementary absorption are described and the construction and optimization of tandem solar cells based on the combination of these heterojunctions demonstrated. The red‐absorbing heterojunction consists of C60 and a fluorinated zinc phthalocyanine derivative (F4‐ZnPc) that leads to a 0.1–0.15 V higher open circuit voltage Voc than the commonly used ZnPc. The second heterojunction incorporates C60 and a dicyanovinyl‐capped sexithiophene derivative (DCV6T) that mainly absorbs in the green. The combination of both heterojunctions into one tandem solar cell leads to an absorption over the whole visible range of the sun spectrum. Thickness variations of the transparent p‐doped optical spacer between both subcells in the tandem solar cell is shown to lead to a significant change in short circuit current density jsc due to optical interference effects, whereas Voc and fill factor are hardly affected. The maximum efficiency η of about 5.6% is found for a spacer thickness of 150‐165 nm. Based on the optimized 165nm thick spacer, effects of intensity and angle of illumination, and temperature on a tandem device are investigated. Variations in illumination intensity lead to a linear change in jsc over three orders of magnitude and a nearly constant η in the range of 30 to 310 mW cm−2. Despite the stacked heterojunctions, the performance of the tandem device is robust against different illumination angles: jsc and η closely follow a cosine behavior between 0° and 70°. Investigations of the temperature behavior of the tandem device show an increase in η of 0.016 percentage points per Kelvin between −20 °C and 25 °C followed by a plateau up to 50 °C. Finally, further optimization of the tandem stack results in a certified η of (6.07 ± 0.24)% on (1.9893 ± 0.0060)cm2 (Fraunhofer ISE), i.e., areas large enough to be of relevance for modules.

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Section: Comparison Of Single and Tandem Devicesmentioning

confidence: 99%

Section: Comparison Of Single and Tandem Devicesmentioning

confidence: 99%

Efficient Organic Tandem Solar Cells based on Small Molecules

Riede

Uhrich

Widmer

et al. 2011

Adv Funct Materials

227

144

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“…A powerful method to adjust the BHJ morphology in vacuum processed small molecule based OSCs is to control the substrate temperature ( T sub ) during deposition of the absorber layer. [9][10][11][12] In this contribution, we study the relationship between T sub , nanoscopic morphology of the BHJ and PCE of the fi nal OSC, with both experimental and theoretical methods.We fabricated and characterized BHJ OSCs, where the intrinsic absorber layer is sandwiched between n-doped and p-doped layers (nip OSC) to ensure an unhampered charge transport to the respective contacts. [ 13 ] The intrinsic BHJ absorber layer of such nip OSCs is composed of the dicyanovinyl-substituted oligothiophene derivative DCV5T-Me…”

mentioning

confidence: 99%

Influence of Meso and Nanoscale Structure on the Properties of Highly Efficient Small Molecule Solar Cells

Moench

Friederich

Holzmueller

et al. 2015

Advanced Energy Materials

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To further improve the power conversion effi ciencies (PCEs) of OSCs, it is necessary to understand the complicated photon-to-electron conversion processes in detail. One important challenge is to understand the relationship between controlled processing of high-performance OSCs, the resulting nanoscopic morphology of the absorber layer, and subsequent PCE of the completed device. This multiscale problem can be only tackled by thoroughly characterizing the different length scales, from the sub-nanometer to the centimeter scale, and complementary simulations to obtain comprehensive insight into the microsopic processes involved in every step. [5][6][7] At the heart of a bulk heterojunction (BHJ) OSC is a blend of two or more organic materials forming the absorber layer of the solar cell. [ 5,6 ] The advantage of this blend architecture over a bilayer structure lies in the increased interfacial area between donor and acceptor materials, which increases the dissociation probability of the strongly bound photogenerated exciton (Frenkel exciton). Once separated into free charge carriers at the material interface, the morphology of the blend layer must provide closed transport paths to the adjacent layers for charge extraction. Thus, the solar cell efficiency is highly sensitive to the size and connectivity of a phase to its adjacent layer, as well as the material purity of each domain. [ 7,8 ] Overall, the constraints for an optimal morphology are manifold, requiring a suffi ciently fi ne-grained morphology for effi cient exciton dissociation, but still suffi ciently coarse for an unhampered charge carrier transport. Hence, the BHJ of an effi cient OSC requires a morphology balancing these competing demands. A powerful method to adjust the BHJ morphology in vacuum processed small molecule based OSCs is to control the substrate temperature ( T sub ) during deposition of the absorber layer. [9][10][11][12] In this contribution, we study the relationship between T sub , nanoscopic morphology of the BHJ and PCE of the fi nal OSC, with both experimental and theoretical methods.We fabricated and characterized BHJ OSCs, where the intrinsic absorber layer is sandwiched between n-doped and p-doped layers (nip OSC) to ensure an unhampered charge transport to the respective contacts. [ 13 ] The intrinsic BHJ absorber layer of such nip OSCs is composed of the dicyanovinyl-substituted oligothiophene derivative DCV5T-MeThe nanoscale morphology of the bulk heterojunction absorber layer in an organic solar cell (OSC) is of key importance for its effi ciency. The morphology of high performance vacuum-processed, small molecule OSCs based on oligothiophene derivatives (DCV5T-Me) blended with C 60 on various length scales is studied. The analytical electron microscopic techniques such as scanning transmission electron microscopy, energy dispersive X-ray spectroscopy, highly sensitive external quantum effi ciency measurements, and meso and nanoscale simulations are employed. Unique insights into the relation between processing, morphology...

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“…This typical p-i-n structure turns out to be flexible for optimizing the absorption of the active layers, choosing the right kind of contact materials as well as the order of the layers. In recent years, this kind of p-i-n configuration is proving to be a versatile concept for investigating the fundamental processes as well as optimization of OSC devices [481].…”

Section: Impurity-doped Os P-n Junctionsmentioning

confidence: 99%

“…In contrast, aromatic molecules such as ortho-chloranil, TCNQ, and dicyano-p-benzoquinone (DDQ) were used in doping phthalocyanines, stacked phthalocyanines, and oligothiophenes [463][464][465][466][467] but less effectively. In the last few years, systematic investigations were carried out to understand the underlying doping physics, which led to the development of OLEDs [468][469][470][471][472][473][474][475][476][477][478][479][480][481].…”

Section: Impurity-doped Os P-n Junctionsmentioning

confidence: 99%

Organic semiconductors for device applications: current trends and future prospects

Ahmad

2014

Journal of Polymer Engineering

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Abstract:With the rich experience of developing silicon devices over a period of the last six decades, it is easy to assess the suitability of a new material for device applications by examining charge carrier injection, transport, and extraction across a practically realizable architecture; surface passivation; and packaging and reliability issues besides the feasibility of preparing mechanically robust wafer/substrate of single-crystal or polycrystalline/ amorphous thin films. For material preparation, parameters such as purification of constituent materials, crystal growth, and thin-film deposition with minimum defects/ disorders are equally important. Further, it is relevant to know whether conventional semiconductor processes, already known, would be useable directly or would require completely new technologies. Having found a likely candidate after such a screening, it would be necessary to identify a specific area of application against an existing list of materials available with special reference to cost reduction considerations in large-scale production. Various families of organic semiconductors are reviewed here, especially with the objective of using them in niche areas of large-area electronic displays, flexible organic electronics, and organic photovoltaic solar cells. While doing so, it appears feasible to improve mobility and stability by adjusting π-conjugation and modifying the energy bandgap. Higher conductivity nanocomposites, formed by blending with chemically conjugated C-allotropes and metal nanoparticles, open exciting methods of designing flexible contact/interconnects for organic and flexible electronics as can be seen from the discussion included here.

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Increase in internal quantum efficiency in small molecular oligothiophene: C60 mixed heterojunction solar cells by substrate heating

Cited by 62 publications

References 11 publications

Efficient Organic Tandem Solar Cells based on Small Molecules

Efficient Organic Tandem Solar Cells based on Small Molecules

Influence of Meso and Nanoscale Structure on the Properties of Highly Efficient Small Molecule Solar Cells

Organic semiconductors for device applications: current trends and future prospects

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