Colors of Life and Optoelectronics: Zinc Porphyrins for Light-Emitting Electrochemical Cells and Organic Photodetectors

Doktorsavhandling, 2020

The field of organic optoelectronics constitutes an interdisciplinary field that covers chemistry, physics, materials science and biology. The technological promises of the organic materials over their inorganic counterparts include a lower production cost and the feasibility to be processed through solution-based techniques on large-area and/or flexible substrates. Among organic optoelectronic devices, two technologies are discussed in this thesis. Those are light emitting electrochemical cells (LECs) and photomultiplication (PM) type organic photodetectors (OPDs). The LEC is a light emitting technology that has attracted a lot of scientific interest due to its simple device architecture and fabrication. A category of LECs that is of high interest, are those LECs consisting of materials emitting near-infrared (NIR) light. This specific field is highly alluring, due to the unique applications NIR light can generate in a wide range of fields from medicine to optical communications. However, organic NIR emitters are inherently of lower efficiency when compared to other wavelengths, thus posing a challenge in material design. Hereof, an attempt was made in the context of this work to design and synthesize emitters that will produce light in the deep NIR region and in a functional LEC. The problem of high aggregation of NIR emitters was tackled by blending with appropriate host materials. On the other side, PM type OPDs aim in sensing and not in the production of light. The characteristic of this special category of OPDs is the possibility of enhancing the received weak signal without the need of external components in the device, like photomultiplier tubes. However, since this specific field is not mature yet, there is not adequate knowledge in material design. Thus, there is a need in discovering the materials that will lead to photomultiplication enabling the construction of more efficient devices in the future. In order to achieve all the accomplishments that will be discussed in this thesis, there was a category of molecules that was the heart of all studies. These molecules, often called as colors of life, due to their importance in many processes occurring in nature were porphyrins. Porphyrins are highly versatile motifs and were the tools that led both into production of deep NIR light but also into improving the detection of weak light.