Given the pressing need to optimize green and low-cost energy sources on a warming planet, one promising area of research is in semiconductors known as organic photovoltaic devices (OPVs), which generate electricity from sunlight. Research at the Nguyen Lab applies principles of materials science, engineering, physics, and chemistry to fabricate and characterize a variety of these devices, including organic solar cells. In order to optimize OSC performance, various device properties must be measured, including efficiency, stability, and overall cost of production. Specifically, these properties are often studied in the photoactive layer, the light-absorbing part of the OSC containing a small molecule electron acceptor and polymeric electron donor intermixed to facilitate electron transport across the device. My summer project aims to understand the stability of a non-fullerene electron acceptor, COTIC-4F, through UV-Vis spectroscopy, profilometry, and data analysis. These methods are used to determine glass transition temperature (T_g), the temperature at which a polymer breaks down from a glassy state to a rubbery state and thereby affects solar cell conductivity. By taking consistent measurements of the T_g, we can more accurately understand the lifetimes and long-term stability of active layer materials.