Neuentwickelte Pentacene Derivate für die Singulett Fission Forschung: Theorie, Fotophysik und Anwendung in Farbstoff- Sensibilisierten Solar Zellen

Abstract

As technology evolves, the production of energy is moving towards more efficient and less harmful methodologies. Using solar energy conversion architectures, which take into account the lessons learned in 50 years of solar energy research, a new set of organic-based sensitizers in conjunction with highly customizable semiconductor materials is being developed. The fields of singlet fission and dye-sensitized solar cells combined means a novel field for solar energy conversion. As such, singlet fission represents a novel photophysical process with high yield of produced charges and the latter is a specific architecture based on the electrochemical potentials of the components herein. In order to understand the theory behind the high quantum yield, several theoretical and computational methodologies were applied. To corroborate energies, electrochemical potentials and state dynamics several spectroscopic techniques such as steady state absorption and emission, as well as transient absorption spectroscopy were applied. Lastly, the design, construction and implementation of solar cells architectures were undertaken. The thesis herein develops and summarizes a set of investigations with the aim of applying advanced techniques and learn about novel photophysical concepts by implementing those concepts into state-of-the-art prototypes for the solar industry. This looking to demonstrate a proof of concept and give a rational explanation of the process. After a short introduction and theoretical considerations to properly understand the presented photophysical, and experimental concepts, the investigations presented herein are divided in three main parts. The first part of the thesis aims to optimize the electron transfer process between the interlayers in dye-sensitized solar cells by means of implementing carbon allotropes. As well, to characterize important factors and obtain data via current-voltage measurements, electrochemical impedance spectroscopy, and photon-to-current spectra. From the latter follows several investigations with the aim of understanding singlet fission from a solution and pure photophysical stand point. That is, understanding the intrinsic dynamics and necessary energetic requirements to obtain the highest quantum yield via optical spectroscopy and computational methods. Looking into several novel pentacene derivatives to unravel effects on singlet excited states and triplet excited states, as well as the singlet fission mechanism. The last section, is the implementation of the pentacene-dyes into a dye-sensitized solar cell architecture. The photophysical characterization of the singlet fission dyes in the solid state and coupled to a semiconductor is novel and paves the road towards better singlet fission dyes, which can produce quantum yields close to 200% and transfer most of their yield in charges to the semiconductor, hence providing close to double of the current in the device