Characterization and Optimization of Organic Solar Cells for Agrivoltaic Applications

One of the distinctive features of organic solar cells is the ability to selectively absorb light within specific wavelength ranges. For that reason, they can be designed to mainly absorb light outside the visible spectrum, while simultaneously transmitting visible wavelengths. This ability makes them a perfect fit for semi-transparent applications such as tinted windows and agrivoltaics.\\ In agrivoltaic applications, it is important to reach a sufficient transparency level, in order to minimize negative effects on plant growth. This transparency can be quantified by the growth factor, which represents the weighted percentage of light transmitted through the cell, based on the wavelengths that are most relevant for plant growth. While the requirements vary for different plant species, a minimum growth factor of 60% is recommended to support the growth of a variety of plants, for example, basil. The main goal of this work is to evaluate materials and develop a stack configuration that can reach this targeted growth factor. In this process, several absorber materials were analyzed for their compatibility to achieve such a high growth factor. Afterwards, stack configurations were developed using the best suited blend, PV-X Plus, as the absorber material. The main feature of these stacks is the back electrode that was designed to maximize the reflection of near-infrared (NIR) light back into the absorber material while transmitting visible light. This was done using several layers of metal oxides and other materials to form a dielectric Bragg reflector (DBR). The layer thicknesses for each material were optimized using the transfer-matrix method (TMM) in a Python-based code, to maximize the growth factor. The results of the simulations were then experimentally recreated. As a result, a growth factor of G = 61.6% and a power conversion efficiency (PCE) of 3.5% were experimentally achieved. The study demonstrates the potential to use semi-transparent organic solar cells for agrivoltaic applications. It also indicates, that the most limiting factor, to further improve the transparency and power conversion efficiency, remains the absorber material.