Structure-Function Relationship in Hybrid Organic / Quantum Dots Photovoltaics

Laying the scientific groundwork for a range of hybrid devices through the development of more efficient and environment friendly photovoltaic cells.

The extension and further development of photovoltaics is essential to reduce the carbon footprint of industrialized nations by 2050.  This implies that all forms of harvesting solar energy must be exploited.  Since there is no clear front-runner in low-cost alternative photovoltaic devices, it is important to pursue all possible avenues.  Hybrid organic / quantum dots solar cells have many advantages and therefore have the potential to supplement energy production of silicon based solar cells.

Similar to many new alternative photovoltaic concepts, the scientific basis of hybrid photovoltaics is weak.  Despite more than a decade of research, highly performing hybrid organic / quantum dots photovoltaic devices are optimized by “trial-and-error” processing.  In particular, detailed knowledge how the processing of device ingredients determines materials assembly and how different material assemblies affect electronic properties is currently missing.  Trial and error approaches, while often effective, have the disadvantage that a change in parameters or the discovery of new materials requires the renewal of often-lengthy device optimization protocols.

We study promising hybrid organic / quantum dots technologies with the goal of unraveling the way in which structure formation during processing affects device performance. The aim is to gain a fundamental understanding of the formation of mesoscopic morphologies within the photoactive layers and their formation kinetics. The principally employed techniques encompass a range of advanced synchrotron X-ray scattering techniques, employing state-of-the art synchrotrons and in-house instruments. The large amount of data acquired by the extensive use of these methods requires the implementation of automatized data analysis methods, modelling and simulation the development of which is addressed within the Big Data project.

Nanocrystals quantum dots (NCQD) are important semiconductor materials for photovoltaics, but their performance is hampered by electronic defects arising from low-energy states in the semiconductor band gap caused by crystal defects. NCQD processing affects the structural order within these nanocomposite materials, leading for instance to a nanometer-scale rearrangement of NCQDs during ligand exchange. Structural properties within these nanocomposite films are thus dramatically affected during the passivation process that has the aim to reduce electronic defects, but the link between structural ordering and chemically induced functionalities remains unexplored to date. Achieving long-range structural order in NCQDs-based photovoltaics is likely to control both device stability and efficiency in this photovoltaic system. Our research addresses the currently lacking of fundamental understanding of the structure-function relationship in these hybrid photovoltaic devices. 

Blending semiconducting polymers with NCQDs, is likely to increase the overall performance of hybrid photovoltaic technologies. 

Our research is contributing to a deeper understanding of the different structural symmetries forming within photoactive hybrid organic / quantum dot films, shedding light on the unknown relationship between chemical processing and induced ordering within the hybrid photovoltaic systems.

The application of NCQDs in combination with polymers has proven to be extraordinarily effective. Further advances in overall efficiency are expected by extending the electronic functionalities through the fundamental understanding of the structural properties of NCQDs and broadening this concept to the organic semiconductors, which will have a high impact within the energy field, with relevant technological implications.

Our research is thus aiming to make a significant contribution to the field of sustainable energy generation, through the development of more efficient and environment friendly photovoltaic cells that can replace fossil energy generation, in order to reduce the worldwide reliance on fossil fuels. Our research falls into the segment of low-cost solar cells devices that can be processed at low temperatures, and making use of industrial established printing processes. The purpose of our studies is thus to lay the scientific groundwork for a range of hybrid devices.

Adolphe Merkle Institute - Chemin des Verdiers 4 - CH-1700 Fribourg - Phone +41 26 300 9254