PhD projects

Organic photovoltaic (OPV) technology represents a crucial pathway toward sustainable energy solutions, offering mechanical flexibility, lightweight, and the potential for seamless integration into buildings, vehicles, and textiles. Recent breakthroughs, particularly in narrow bandgap non-fullerene acceptors (NFAs) and high mobility donor polymers, have elevated OPV power conversion efficiencies from below 1% to above 21%. Despite these advances, translating lab-scale developments into scalable, industry-compatible manufacturing remains a major challenge.

This PhD project aims to develop roll-to-roll (R2R) printed organic photovoltaic modules by leveraging state-of-the-art organic semiconducting materials. The focus will be on industry-compatible large-area printing techniques, including slot-die coating, flexographic printing, gravure printing, and sputtering for sequential deposition of functional OPV layers. The PhD work will be dedicated to SUNTEX project.

For the SUNTEX project, the focus will be on innovating fully printed semi-transparent OPV devices designed to be integrated as flexible tapes woven into high-tenacity yarn textiles. These lightweight solar textiles will be developed for tensile architecture, textile shade structures, and facades that simultaneously harvest solar energy and provide sun shading. The semi-transparent OPV foils will incorporate metal oxide-based distributed Bragg reflector (DBR) stacks, light management layers such as photonic architectures and anti-reflective coatings, as well as metal oxide barrier layers for enhanced optical control and environmental protection, ensuring both functionality and aesthetic appeal in urban architectural applications.

Meanwhile, another focus point will be to optimize indoor OPV devices for low-light environments by developing a high-power conversion efficiency (PCE) fabrication process through R2R techniques. These indoor devices will feature advanced passivation layers, including Polyfullerene and tris(phenylamino)phenothiazine (TPAP), to suppress interfacial recombination and maximize indoor performance. Throughout, environmental sustainability will be prioritized by adopting green solvents and minimizing process waste to ensure scalable and responsible manufacturing.

PhD Student: Abhinav Chandel
Supervisor: Morten Madsen

PhD student: Fathimath Faseela
Supervisor: Morten Madsen

Organic photovoltaics (OPVs) are an emerging light-conversion technology for clean energy generation. Non-fullerene acceptors (NFAs)-based OPVs have achieved over 19% efficiency but they suffer from short shelf lives and limited operational lifetimes. The decline in device performance with time can be partly attributed to morphological degradation and photodegradation.

NFAs can be categorized as small molecules, polymers, and larger structures. While degradation mechanisms and stabilization methods have been extensively studied in polymer donor: small-molecule NFA systems, less emphasis has been placed on other organic photoactive materials, such as small molecular donors and polymer acceptors.

The project aims to investigate the photochemical and morphological degradation mechanisms of state-of-the-art OPV materials, including small molecule donors and polymeric acceptors. The feasibility of using antioxidants in the active layer will also be investigated by analysing the interactions their interactions with both the active layer and the OPV interlayers. Overall, the project seeks to extend the operational lifetime of OPV modules and develop a structural-dependent degradation understanding of degradation mechanisms. This research is part of the OPVStability Marie Skłodowska-Curie Actions Doctoral Network (MSCA-DN).

PhD student: Hsuan-yu Wang

Supervisor: Vida Engmann

Energy production by renewable energy sources that can generate sufficiently large amounts of energy to supply the world’s needs is urgently needed. Solar energy, as one of the most promising renewable sources, can be harnessed by photovoltaics (PVs) that directly convert sunlight into electricity. Recently, organic photovoltaics (OPVs) are emerging due to their low-cost fabrication, mechanical flexibility, low environmental impact, short energy payback times and high demonstrated Power Conversion Efficiency (PCE) of 19%.

OPVs based on low-gap non-fullerene acceptors (NFAs) absorb primarily in the near infrared (NIR) region and can be designed to let visible light pass through the cell. Hence, these solar cells can potentially be used in a semitransparent device, which can be integrated into windows of buildings or greenhouses to generate substantially large amounts of energy with net zero energy consumption. However, stability issues remain, which still hinder the large-scale commercialization of OPV materials.

The PCE of a solar cell can be improved by forming a tandem structure that stacks two or more semiconductors with complementary band gaps. In the case of a semitransparent solar cell, tandem devices have to be visually transparent. One way of constructing such devices is to have a bottom cell based NIR NFAs and a top cell that absorbs primarily in the near ultraviolet (NUV) range, so that photons in the visible range are not absorbed. Metal oxides are typically stable, non-toxic and can be manufactured with low-cost techniques, making them appealing candidates as a top cell in a tandem transparent solar cell. Nevertheless, most oxides are n-type semiconductors and exhibit a band gap of >3 eV that is too wide to absorb a significant portion of the solar spectrum. Band structure engineered low gap (2<Eg ≲2.5 eV), stable and non-toxic oxide semiconductors using earth-abundant elements could potentially be used as a top cell in an OPV-based tandem device to harvest UV photons, and thus construct a unique low-cost, stable and highly efficient semitransparent solar cells with PCEs >11% and average visible transmission (AVT) of >53% (beyond state-of-art).

This PhD project aims to develop novel low-cost and stable oxide/OPV semitransparent tandem PV with beyond state-of-the-art performance. New oxide alloys with tunable band gaps will be synthesized using magnetron sputtering. The electronic, optical and transport properties of the alloys will be characterized with a particular focus on tuning the band gap and band edges by varying the alloy composition. Then n- and p-type doping of the alloys will be explored to optimize them for PV devices and semi-transparent tandem solar cells. Finally, an oxide/OPV transparent tandem solar cell will be fabricated and evaluated.

PhD student: Kun Wang

Fossil fuels are the cause of smog, oil spills, ocean acidification and climate change. Their extraction breaks and poisons the earth. When we buy them, we fund dictators and autocrats the world over. Fossil fuels are also running out.

There therefore is a great need for new ways of producing large amounts clean renewable energy. A long running favorite for this is solar. However current solar cells, based on silicon, is expensive, have a long energy payback time and are commonly seen as an eyesore.

A promissing alternative is semi-organic solar cells based on organic semiconductors and metal oxides. They require far less energy to produce and are as a result cheaper with a shorter energy payback time. They can also be made transparent such that they can just replace windows in building design, no more eyesores!

Transparent solar cells are not just for aesthetics though. They would also be great materials for building greenhouses since plants only use a thin spectrum of red light meaning we could use land for both farms and clean energy production.

Semi-organic solar cells can be transparent by using the large bandgap of the metal oxide to absorb the UV-light and the small bandgap of the organic semiconductor to absorb the infrared light converting both into electricity while letting the visible light pass through. However, producing them will require some combination of doping, control over interface morphology, controlled stoichiometry, insertion of thin interlayers and possibly other means. This project seeks to unite all these in order to produce high quality semi-organic solar cells for scalable production.

PhD student: Martin Asbjørn Krehbiel

Supervisor: Morten Madsen