By Michela Prete
Organic solar cells (OPVs) are considered, nowadays, a promising alternative to the inorganic PVs thanks to their low fabrication cost, the easy processability and tunability to different applications. In respect to the latest, organic materials allowed, in fact, the fabrication of flexible and stretchable devices opening the door to the possibility of mass production. These advantages are still limited by the ongoing improvement on the stability and efficiency of the organic devices. Although the efficiency has reached 12%, the final commercialization of the OPVs is still dependent on their stability. If different have been, in the past years, the photochemical stability studies, still few are the reported analysis on the mechanical properties of the organic devices. It is very important to understand the mechanical properties of the materials utilized, as much as understanding the results of the mechanical stress on flexible cells that is affecting the performances of the device over time. The main goal of the research project is to gain insight into the mechanical properties of flexible organic solar cells and to explore the possibilities of increasing the mechanical durability and stability of the cells while maintaining scalability and high electrical device performance. The project therefore encompasses work and specific objectives on determining the influences from both photochemical and mechanical stressing of flexible organic solar cells, and on applying specific additives that stabilize the cells against these degradation factors, both individually and combined. The work builds upon initial work on photochemical stabilization of organic solar cells, from where the initially tested photochemically stabilizing additives are chosen.
Supervisors: Morten Madsen and Vida Engmann
Hyperspectral thermal camera
By Anders Christian Løchte Jørgensen
This industrial PhD project is conducted in a collaboration between Newtec Engineering A/S and SDU. It focuses on the development of a hyperspectral thermal camera that can be used for thermography of buildings. Thermography of buildings is used to determine energy classification and find areas of poor thermal isolation. Present day thermal cameras only allow acquisition of greyscale images showing the intensity of infrared light in each pixel. This approach neglects the varying emissivity of materials which causes incorrect temperature measurements. In contrast, a hyperspectral camera measures the infrared light intensity at several wavelengths generating a full spectrum in each pixel in the ideal case. With this information, it will be possible to recognize a material through its emissivity, and thereby get a more accurate temperature determination. The project includes experimental work to develop and characterize the essential components for the camera. This includes the development of a graphene-based infrared sensor and of a multi-layered thin film mirror for a Fabry-Pérot interferometer used for spectral filtering. The sensitivity of the graphene sensor will be optimized by using quantum dots and plasmonics active in the infrared regime.
Supervisor: Jakob Kjelstrup-Hansen
Spider silk as model superior biomaterials
By Irina Iachina
Spider silk has extraordinary mechanical properties compared to most man-made materials. For example, the tensile strength of spider silk is comparable to that of steel alloy however it weighs far less and can be spun at room temperature. Due to this unique combination of strength and extensibility dragline silk has been extensively studied ]. It is however, near impossible to obtain spider silk in industrial amounts. Therefore, much research has gone into development of artificial spider silk, which can be spun from an aquamelt in an extremely efficient process. Artificial spider silk would be an environment friendly and strong substitute useful in many industrial purposes and environment friendly process. Large scale production of high-quality artificial silk has not been possible so far, and a full understanding of spider silk from molecule to macroscopic fiber is still lacking. The overall aim of this project is to design artificial silk with the same or better properties as natural spider silk. To do this we propose to develop new methods for the synthesis of artificial spider silk fibers using the acquired knowledge regarding the complex nanostructure of the natural silk and a novel microfluidic based biomimetic fiber spinning technique.
Supervisor: Jacek Fiutowski
3D Nanomaterials: Fabrication, Properties and Smart Applications
By Reza Abolhassani
Nanoscale materials with multifunctional properties have received increasing interest in scientific and industrial communities because of their versatile applications in advanced technologies. A new class of nanomaterials, so called smart materials, has been recently emerged as very potential candidates for various applications because of their capability to self-respond to any external stimuli (e.g. stress, temperature, light, electric or magnetic field, deformation, electrochemical, pH, etc.) by altering their one or more properties in form of a reliable read out signal. Their extensive applications in healthcare, aerospace, automotive, electronic, smart polymers, smart textile, sensors, medicine, and etc. makes it essential to study and research on this young novel technology. Nanomaterial fabrication in the desired compact form is the most important prerequisite for any scientific and technological development, and nowadays, the key challenge is to design the nanomaterial in 3D complex smart forms which are equipped with right functions and simultaneously are easy to utilize.
The aim of this PhD project is to synthesize 1D ZnO nanostructures based complex shaped nanostructures and selectively surface engineering of arm morphologies using state-of-the-art micro- and nanofabrication methods for enhancing their optical, electronic, chemical, and mechanical properties which will be carefully characterized, analyzed, and understood. The structure-property relationships of these materials will be understood, and they will be explored for applications in various smart technologies in direction of optics, catalysis, energy, sensing, and smart textiles, and they will be utilized for various possible applications.
Supervisor: Yogendra Kumar Mishra
X-ray and neutron scattering studies of metal oxide interlayers for photovoltaic applications
By Mariam Ahmad
Organic solar cells (OSCs) have gained a lot of popularity during the last 10 years since they are light weight, have a flexible structure and can be produced at low cost. These properties make OSCs promising candidates for cheap mass production as opposed to their commonly used inorganic counterparts. OSCs have not yet been industrially implemented for energy production due to challenges in obtaining high power conversion efficiencies but with the latest OSCs reaching efficiencies above 17 %, it is only a question of time before OSCs can be mass produced and implemented for cheap and sustainable energy production. One main challenge that the current OSCs are facing is obtaining long-term device stability. The current OSCs are prone to degradation over short time, which makes them ineligible for mass production in their current state. More research in device stability of OSCs is therefore needed before mass production can become a reality. The implementation of sputter deposited metal oxide interlayers such as MoOx and TiOx as charge-selective transport layers in OSCs has shown a higher long-term stability and an overall better device performance. These metal oxides will be the focus of this PhD project. The aim of the project is to develop sputtered MoOx and TiOx thin films for OSCs and study their detailed structure and properties using X-ray and neutron scattering at large-scale facilities. The degradation process will be studied upon subjecting the metal oxides to heat, light and oxygen and the electronic properties of the metal oxide interlayers will be studied using XPS and X-ray absorption. Device fabrication of OSCs containing the metal oxides will also be part of this project. The project is a part of the SMART (Structure of Materials in Real Time) lighthouse consortium.
This project is conducted in collaboration with Aarhus University, Prof. Bo Brummerstedt (Head of the UFM ’SMART’ ESS lighthouse) and Paris-Sorbonne University, Prof. Nadine Witkowski.
Supervisor: Morten Madsen
High-accuracy prediction of meat expiration dates by overcoming non-linearity barriers for microcantilever biosensors
By Lawrence Nsubuga
There is a yearly waste of 137,500 tons of meat and fish products in Denmark, of which about 43,000 tons are wasted due to overly careful expiration date estimations, resulting into high carbon emissions. Today households, restaurants, catering, and food stores rely on the printed expiration date, which is based on general prediction curves for meat degradation. For example, for pork cuts at 5°C under aerobic conditions the prediction curve says 8 days (+/-) 3 days. So, to be on the safe side, expiration dates are set to 5 days. The only means to control actual freshness of meat products are microbiological tests conducted at external laboratories requiring shipping of samples, growing, and counting bacteria. Such tests are seldomly carried out, since they are expensive (app. 335 € /sample), time consuming (48 hours) and do not predict the exact expiration date. There are other analysis methods available, but they all need to be carried out at external laboratories, e.g., measurement of cadaverine levels using gas chromatography mass spectrometry. Cadaverine is a volatile biogenic amine providing an exact measure for meat spoilage level. The amount of cadaverine gas increases in a predictable way over time depending on the type of meat. This PhD project proposes to realize great potential for CO2 reduction, by development of a biosensor for cadaverine in meat, enabling on-site highly accurate prediction of meat expiration dates. The main objective is to develop a biosensor enabling precise measurements of low levels of cadaverine and use this to predict meat expiration dates. Very small differences in cadaverine levels, at an early deterioration stage, translates into large differences with respect to expiration date. Therefore, it is a strict requirement that the biosensor enables high-accuracy measurements of +/- 10% at low levels of cadaverine, down to 10μg per kg of meat. To achieve this, we must overcome current state-of-the-art barriers; that microcantilevers provide nonlinear responses and that mathematical response processing models for nonlinearity compensation are lacking. The research hypothesis is that an array of microcantilever beams in different sizes or with different coatings, leading to different characteristic frequency modes, will enable dynamic real-time monitoring of an array of constants that can be fed into a mathematical model developed for non-linearity compensation.
Supervisor: Roana Melina de Oliveira Hansen
Industrial Roll-to-Roll Manufacturing of Solution-Processed, Non-Fullerene Based Organic Photovoltaics
By Le Lena Maria Nguyen Ngoc
Over the past two decades, organic photovoltaics (OPV) has been dominated by fullerene acceptors. However, their development faces some drawbacks as the materials show limitations in terms of synthetic flexibility, long-term stability (e. g. easy aggregation), large energy offsets for free charge carrier generation and weak absorption in the visible and near infrared (NIR) region. Non-fullerene acceptors (NFA) mainly overcome these drawbacks. Their optical and photophysical properties can be easily modified due to molecular engineering which allows for the tunability of the absorption and energy levels which open up a wide range of opportunities for applications. Choosing specific donor and acceptor combinations with complementary absorption thus allows for higher current output and tuning of the energy levels will lead to an increase in device voltage. Therefore, NFAs are very interesting candidates for industrial OPV as they promise a high power conversion efficiency (PCE). According to literature, PCEs of current state of the art NFA based OPV over 18% have been reported. Having said this, such efficiencies have solely been obtained for small lab-scale devices (<< 1 cm2), commonly fabricated under inert atmosphere, using non-benign solvents and a combination of solution-processing and evaporation techniques. All the aforementioned is not compatible with industrial manufacturing. The aim of this PhD project is the fabrication of long-lasting and large-scale organic photovoltaics based on high-efficiency NFA systems in a roll-to-roll operational environment. The focus will be on the evaluation of new material systems for possible industrial use which includes optimization of the device architecture, layer morphology, coating uniformity and long-term stability. Optical, electrical and morphological characterizations will be performed to understand charge carrier dynamics of the studied NFA systems. This project is an industrial PhD project at Armor solar power films GmbH and conducted in collaboration with SDU.
University Supervisor: Prof. Dr. Morten Madsen
Industrial Supervisor: Dr. Sebastian Meier
The stretchable OLED display
By Jes Linnet
Flexible optoelectronic devices such as light-emitting diodes (LEDs) typically consist
s of a multilayer structure deposited on a flexible substrate. The active layers are often based on organic semiconductors that can be made with excellent optoelectronic properties and have some mechanical flexibility. Several companies are developing flexible OLEDs for displays and lighting. However, such devices are only bendable, but they are not stretchable: they can be bent to a certain radius of curvature, but pure strain beyond a few percent will lead to immediate failure, and they can therefore not be mounted on a 3D-surface. The aim of this project is to develop stretchable organic light-emitting diodes and ultimately realize a business card-sized display. The approach in this project, to resolve the strain limitation, is based on a substrate with specially designed surface corrugations. Upon stretching the substrate, these corrugations flatten out, and locally the surface only bends. The outcome will be OLEDs that can conform 3-dimensional surfaces for lighting and display applications within a range of product areas. The specific objectives are to design and develop an elastomeric substrate with a surface corrugation pattern that allows substrate stretching without significant surface strain and to realize an OLED display layer stack on top consisting of a transparent bottom electrode, a sandwich structure of several organic semiconductor materials for hole/electron balancing and light emission, and a top electrode. Furthermore, an encapsulation solution will be developed and implemented to protect against degradation that results from exposure to ambient conditions. This project is an industrial PhD project; a collaboration between SDU and Polyteknik.
Supervisor: Jakob Kjelstrup-Hansen