Light polarization in single molecule spectroscopy: From visualization of structural anisotropy and energy transfer to super-resolution imaging with orientational contrast

Abstract: ?-conjugated polymers are an important class of materials which can be used in e.g. photoelectric (solar cells) or electroluminescent (displays) devices. These materials are implemented in a number of applications these days since a lot is already known about them. There is, however, still a lot to learn in order to increase the efficiency and reduce the power consumption of devices. There are many different tools which can be used in experiments. Several of these tools are typically used for characterization as they complement each other. The work presented in this thesis utilizes a wide-field microscopy technique which allows studying matter at the single molecule level. In some aspects this is a great advantage as it allows characterizing the underlying distributions of properties of materials. Interactions between neighboring molecules can be reduced which gives access to important information which otherwise would be hidden. By addressing underlying distributions information about which properties to pay the most attention to might be provided. A broad distribution of a property could efficiently prevent optimization of a parameter as it could result in that only an insufficient number of molecules are addressed. However, spectroscopic properties of conjugated polymers are in many cases closely related to the polymer chain conformation. Polarization spectroscopy is the most used tool in the work presented here. The polarization of light reveal different organizations of materials which is turn is relevant for e.g. energy transfer properties.