- This work aims to broaden use of the organic semiconductor pentacene (Pn) by means of improving its oxidation and photodimerization stability. In particular, we study the photophysical properties of functionalized Pn derivatives with side groups R in amorphous thin film, referred to as Pn-R-F8 when fluorinated. Using the optics experiments presented in the following chapters, we found that side groups (tricyclohexylsilyl)-ethynyl (TCHS) are more effective at preventing degradation under visible light than side groups (triisopropylsilyl)-ethynyl (TIPS). We also demonstrate how host polymers matrices made of either poly-(methyl methacrylate) (PMMA) and poly-(vinylidene difluoride) (PVDF) can be used to protect organic semiconductors without complicating sample preparation. Additionally, we explore how the average intermolecular spacing of Pn-R-F8 in the host polymer matrix affects the film's photoluminescence (PL) spectrum and photodegradation dynamics. We also found that the wavelength of incident light changes the primary chemical pathway for Pn-R-F8 decomposition, as ultraviolet (355 nm wavelength) light favors photodimerization while visible (633 nm wavelength) light catalyzes endoperoxide (EPO) formation. Finally, we demonstrate that thermolysis can reverse EPO formation in Pn-R-F8 films and restore lost functionality.