PhD projects

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.

PhD student: Mariam Ahmad

Supervisor: Morten Madsen

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 optimisation of the device architecture, layer morphology, coating uniformity and long-term stability. Optical, electrical and morphological characterisations 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.

PhD student: Le Lena Maria Nguyen Ngoc

University supervisor: Morten Madsen
Industrial supervisor: Dr. Sebastian Meier

In the age of climate change and the scarcity of fossil raw materials, the renewable energies must increasingly be used. Although classic inorganic solar cells have proven themselves and production costs are steadily being reduced, research interest is increasingly directed towards alternative materials for converting light energy into electrical energy.

Organic semiconductors offer several advantages over inorganic variants: low production costs, high absorption coefficients, easy processability and flexibility; which make them one of the most promising candidates for photovoltaics and photocatalysis. The key challenge that remains to be overcome to make organic photovoltaic (OPV) devices competitive is their limited photostability and hence relatively short lifetimes.

This PhD project is part of the Carlsbergfondet project Artplast - Artificial Chloroplasts: Nature-inspired electronic molecular nanoparticle platform with the focus on developing highly efficient material systems for hydrogen evolution and solar electricity generation by mimicking the energy converting and self-healing mechanism of a leaf.

The goal of the project is to develop an artificial chloroplast using conjugated donor:acceptor:antioxidant nanoparticles. By testing and controlling the fundamental photophysical and photochemical properties, the morphology vs. electrical properties relations in these materials will be identified and it will be used to tailor highly efficient material systems for hydrogen evolution and solar electricity generation, thus contributing to the transition of the current energy system to zero emission society based on renewable resources.

PhD student: Rovshen Atajanov

Supervisor: Vida Engmann

Solar intermittency is a great drawback for solar energy conversion systems. By harvesting solar irradiation in the form of hydrogen bonds, the energy can be stored and transported. The active layer in organic solar cells (OSC) is the backbone of the devices; it is responsible for light absorption, charge separation and migration.

The use of nanoparticles (NP) as active layers made of conjugated polymer donor (D), non-acceptor-fullerene (NFA) and antioxidant (Aox) bulk heterojunction have demonstrated great photo conversion efficiencies and enhanced stability in OSC devices. These NP developed for organic solar cells require the same characteristics as hydrogen production photocatalysts: efficient light-harvesting, charge separation, charge transfer and long-term stability. Yet, this new class of NP materials has not been much explored despite of their extremely high HER activity under visible light.

In this project, we strive to find D:A:Aox NP with suitable thermodynamic and kinetic properties to carry out water splitting. The study and characterisation of these NP will provide the knowledge in this regard to fill the gaps in the development of organic NP for hydrogen production.

PhD student: Miguel Angel Leon Luna

Supervisor: Vida Engmann