Stokes spectroscopy: the development of a novel method to acquire and interpret polarized emission spectra - applications to poly(3hexylthiophene and p(ndi2od-t2)
Optics, as a field of study, has been a critical tool within the discipline of material science for over one hundred years. Through lights interaction with matter, researchers can determine information such as material composition, electronic and physical properties. This information is then used to guide research for specific applications. From the outside, it may seem as though optics as a field is complete; all possible experiments known and possible outcomes interpreted. However, one such property of light, specifically polarization, has proven difficult to measure and subsequently analyze in a meaningful way. Current techniques for measuring polarization information involve simple rotations of a linear polarizer, or analyzer, to get a loose understanding of an emitting sources polarization state. However, this technique and others like it are far from complete and much of the polarization information is still unavailable to researchers. One way to elucidate more polarization information is to implement a method proposed by Stokes in the late 1800s, in which four parameters are used to describe a sources intensity and polarization states. The goal of this work is to show how the addition of the Stokes technique to a typical spectroscopic setup, along with computational fitting, produces direct measurements of these polarization states. Further, we show the capabilities of these adaptations by applying the technique to two organic semi-conducting polymers, Poly(3-hexothilophene) and P(NDI2OD-T2). Doing so has allowed for further elucidation of material properties, including aggregate formation and energy transfer, which is typically unavailable for such materials at high temperature.