Fluxim AG

Feusisberg, Switzerland

Fluxim AG

Feusisberg, Switzerland
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Agency: European Commission | Branch: FP7 | Program: CP | Phase: ICT-2007.3.2 | Award Amount: 3.88M | Year: 2008

White Organic Light Emitting Diodes (OLEDs) are potentially highly efficient large area light sources that can be used for general lighting applications in hitherto unprecedented ways, such as light-emitting flexible foils. In the past years, the luminous efficacy of prototype white OLEDs has shown a very fast, fivefold, increase. In principle, there seems to be no fundamental obstacle towards 100 lm/W efficiency, beyond that of fluorescent lamps. However, in practice the ever-increasing complexity of OLEDs (20 layers or more) now hampers further progress towards that goal, in part because reaching this efficiency goal is only of practical interest in combination with durability, colour stability and tunability, mechanical stability and ease of fabrication. For the further development of efficient white OLEDs, the availability of an experimentally validated opto-electronic device model will be crucial. Todays first generation models, based on conventional understanding of transport and photo-physical processes, are at least incomplete for realistic OLED materials. The AEVIOM project aims at enabling a breakthrough in white OLED efficiency and lifetime by the development and application of an integrated second generation OLED model. After experimental validation, the model will provide a quantitatively correct physical description of the effects of disorder on the transport and photo-physical processes. The model will be the basis for numerical methods that properly include the entire chain of electrical and optical effects inside the organic semiconductor, as well as the optical out-coupling. Finally, experimentally validated recommendations will be given towards the realization of a breakthrough in white OLED efficiency and lifetime, and also in device manufacturing (simplified optimal layer structure).

Agency: European Commission | Branch: FP7 | Program: CP | Phase: ICT-2011.3.6 | Award Amount: 14.46M | Year: 2011

Organic photovoltaics (OPV) represent the newest generation of technologies in solar power generation, offering the benefits of flexibility, low weight and low cost enabling the development of new consumer nomadic applications and the long term perspective of easy deployment in Building Integrated Photo Voltaics (BIPV) and energy production farms. This is a key opportunity for the EU to further establish its innovation base in alternative energies.The current challenges reside in the combination to increase efficiencies to 8-10% (module level), increase expected lifetime up to 20 years and decrease production costs to 0.7 Eur/Wp, while taking into account the environmental impact and footprint.The key project objectives are to achieve:\tPrinted OPV with high efficiency architectures such as tandem cells and dedicated light management structures\tHigh performance photo active and passive (barrier) materials including process controlled morphology\tSolutions for cost effective flexible substrates, diffusion barriers and conductors\tDeep understanding of the device physics, elucidation of degradation mechanisms and estimate environmental impact of the main materials and processesThe project consortium combines industrial, institutional and academic support to make a significant impact at European and International level, especially on materials and processes while demonstrating their market-relevant implementations. The industrial project partners are well assembled along the supply chain of future OPV-based products, which is an important prerequisite for the creation of significant socio-economic impact of this proposal.

Agency: European Commission | Branch: FP7 | Program: CP-FP | Phase: NMP.2011.1.4-5 | Award Amount: 2.16M | Year: 2011

OLED lighting holds the promise of entering the annual global lighting-fixture market that is estimated between $US 50-90 billion. OLED technology provide an environmentally friendly technology that requires no mercury and can enable energy savings up to 90 % (per lamp socket). Global transition to such efficient lighting sources will dramatically reduce energy. Since the onset of the solid state lighting initiative towards the end of last century, the advance in OLED technology has been accelerated by a world-wide investment in material science, process technology, and infrastructure. The technological hurdles are still challenging and numerous, and achieving the target efficiency, colour, colour rendering and lifetime has only partly been accomplished. In the last decade, progress in raising OLED efficiency has stagnated and advanced optical techniques proved to be essential in order to meet the annually growing performance targets. Interest in modelling tools capable of simulating material properties and devices becomes more and more important in order to overcome the remaining fundamental challenges and to accelerate research and development. The overall goal of IM3OLED is the development, evaluation and validation of a predictive multi-scale and multi-disciplinary modelling tool that will accelerate research and development of organic light-emitting diodes for lighting applications. IM3OLED aims to strengthen the leading position of the European OLED Industry by enabling a higher integration level of predictive computational methodologies that accelerate research and development of OLED Lighting technology. Furthermore, accelerated R&D enables an earlier market introduction of OLED Lighting technology in Europe which will create long-term European manufacturing jobs due to the high degree of technical novelty and required specialization.

Knapp E.,ZHAW Zurich University of Applied Sciences | Ruhstaller B.,Fluxim AG
Digest of Technical Papers - SID International Symposium | Year: 2015

A numerical model for charge transport in organic semiconductor devices that accounts for self-heating is presented. In admittance spectroscopy this model reproduces the negative capacitance in bipolar, and more importantly, in single carrier devices. We show that self-heating is crucial not only in large-area OLEDs, but also in small-area devices. © 2015 SID.

Knapp E.,University of Zürich | Ruhstaller B.,University of Zürich | Ruhstaller B.,Fluxim AG
Applied Physics Letters | Year: 2011

We present a comprehensive numerical impedance spectroscopy analysis of an organic semiconductor device. A physical model that considers localized states is combined with a space- and frequency-resolved numerical framework. We study the details of the frequency-dependent capacitance of an electron-only device and distinguish different trapping regimes depending on the parameters. Depending on the choice of the trapping parameters, a capacitance rise at low frequency is observed. The extraction of the characteristic temperature of the exponential of the trap density of states (DOS) by a simplified method by T. Okachi [Appl. Phys. Lett. 94, 043301(2009)] is investigated. © 2011 American Institute of Physics.

Knapp E.,University of Zürich | Ruhstaller B.,University of Zürich | Ruhstaller B.,Fluxim AG
Journal of Applied Physics | Year: 2012

We present an analysis of charge mobility determination methods for the steady as well as the transient state and investigate shallow charge traps with respect to their dynamic behavior. We distinguish between fast and slow trap states in our numerical model corresponding to two characteristic regimes. The two regimes manifest themselves in both impedance spectroscopy and dark injection transient currents (DITC). Further we investigate the charge mobility obtained from dynamic simulations and relate it to the extracted charge mobility from steady-state current-voltage curves. To demonstrate the practical impact of these regimes, we apply our numerical model to the DITC that have commonly been used to determine the charge mobility in organic semiconductor devices. The obtained results from DITC studies strongly depend on the measurement conditions. Therefore we analyze the measurements of reference [Esward, J. Appl. Phys. 109, 093707 (2011)] and reproduce the effects of varying pulse off-times on the transient current qualitatively. Thus, our simulations are able to explain the experimental observations with the help of relaxation effects due to shallow traps. © 2012 American Institute of Physics.

Perucco B.,Fluxim AG | Perucco B.,University of Zürich | Reinke N.A.,University of Zürich | Rezzonico D.,Fluxim AG | And 3 more authors.
Optics Express | Year: 2010

In this paper, numerical algorithms for extraction of optoelectronic material and device parameters in organic light-emitting devices (OLEDs) are presented and tested for their practical use. Of particular interest is the extraction of the emission profile and the source spectrum. A linear and a nonlinear fitting method are presented and applied to emission spectra from OLEDs in order to determine the shape of the emission profile and source spectrum. The motivation of the work is that despite the existence of advanced numerical models for optical and electronic simulation of OLEDs, their practical use is limited if methods for the extraction of model parameters are not well established. Two fitting methods are presented and compared to each other and validated on the basis of consistency checks. Our investigations show the impact of the algorithms on the analysis of realistic OLED structures. It is shown that both fitting methods perform reasonably well, even if the emission spectra to be analyzed are noisy. In some cases the nonlinear method performs slightly better and can achieve a perfect resolution of the emission profile. However, the linear method provides the advantage that no assumption on the mathematical shape of the emission profile has to be made. © 2010 Optical Society of America.

Neukom M.T.,ZHAW Zurich University of Applied Sciences | Neukom M.T.,Fluxim AG | Zufle S.,ZHAW Zurich University of Applied Sciences | Ruhstaller B.,ZHAW Zurich University of Applied Sciences | Ruhstaller B.,Fluxim AG
Organic Electronics: physics, materials, applications | Year: 2012

A method to extract reliable material and device parameters of organic solar cells is presented. We employ a comprehensive numerical device model to simulate the solar cell operation in transient and steady-state condition. Parameter extraction with numerical simulation is error-prone because model parameters are often correlated, their unique determination is very difficult and extracted parameters are likely to be inaccurate. We combine the current-voltage characteristics, the photo-CELIV currents (charge extraction with linearly increasing voltage) and the photocurrent response to a light pulse to reduce parameter correlation and increase accuracy and reliability of the extracted parameters. With a correlation matrix analysis it is shown that parameter correlation is significantly reduced when combining several experimental data sets compared with the analysis of current-voltage curves only. We find a set of parameters to reproduce the complete series of measurements with the numerical simulation. The full electrical behavior can be described using a basic drift-diffusion model with constant mobilities and direct photon-to-charge conversion. With this model we extract charge carrier mobilities in the order of 10-4 cm2/V s, a Langevin recombination prefactor of 0.08, charge injection barriers equal at both sides in the range of 0.25 eV and further device parameters for a BHJ cell with PT5DPP as donor and PCBM (C70) as acceptor. The solar cell is simulated with the extracted parameters and internal distribution of electrons, holes and the electric field are visualized. © 2012 Elsevier B.V. All rights reserved.

Lanz T.,University of Zürich | Fang L.,Korea Advanced Institute of Science and Technology | Baik S.J.,Hankyong National University | Lim K.S.,Korea Advanced Institute of Science and Technology | And 2 more authors.
Solar Energy Materials and Solar Cells | Year: 2012

Thin layers of lithium fluoride (LiF), together with aluminum, can be used as rear electrodes in high-efficiency amorphous silicon (a-Si:H) solar cells on rough substrates, as recently demonstrated by Fang et al. (IEEE Transactions on Electron Devices 58(9)(2011) 3048-3052). We employ numerical modeling to evaluate the optical losses and charge generation profiles in these thin film solar cells. We find that the increase in rear electrode reflectivity by inserting LiF, leading to increased photocurrent, is the dominant factor in device performance improvement, accounting for 7% gain in photocurrent. The simulations are in good agreement with measurements of pin a-Si:H solar cells with varied rear electrodes. © 2012 Elsevier B.V. All rights reserved.

Neukom M.T.,ZHAW Zurich University of Applied Sciences | Reinke N.A.,ZHAW Zurich University of Applied Sciences | Ruhstaller B.,ZHAW Zurich University of Applied Sciences | Ruhstaller B.,Fluxim AG
Solar Energy | Year: 2011

An accurate determination of the charge carrier mobilities is essential to model and improve organic solar cells. A frequently used method to determine charge carrier mobilities is the charge extraction by linearly increasing voltage technique (CELIV). In this technique a voltage ramp is applied to the device in order to extract free charge carriers inside the bulk. The free charge carriers can be created by injection or by a short light flash (photo-CELIV). With a simple analytical formula the mobility is commonly estimated on the basis of the temporal position of the current peak. We simulate the photo-CELIV experiment with a fully-coupled electro-optical model to analyse the accuracy and limitations of the analytical formulas that are used to calculate the mobilities. We show that for thin film solar cells RC-effects are problematic and can lead to inaccurate results. If RC-effects are negligible only the order of magnitude of the fast carrier mobility can be determined using the analytical formula. We measure CELIV currents for several voltage slopes and transient photo-currents of an organic bulk heterojunction solar cell. By fitting our numerical model to the multiple curves we show that important material parameters like the electron mobility, hole mobility, charge generation and recombination efficiency can be determined using numerical parameter extraction. © 2011.

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