In order to acquire the details of the function of an organic solar cell, it is important to understand a number of important physical parameters. From the particular understanding of how the efficiency of an organic solar cell is obtained to the acquisition of parameters such as absorption, exciton diffusion, and charge transfer character, the experimental success of important techniques has driven the conceptualization and construction of new and improved devices. While the measurement of all of the important parameters of an organic solar cell are critical, there are many researchers in the field that heavily focused on the exciton diffusion length of the device. The exciton diffusion length LD in organic polymeric films is often measured using the diffusion-limited quenching at the interface with either fullerenes or fullerene derivatives or metals. Various nonlinear optical techniques have been used to probe intramolecular interactions in solar cell materials.