In the past years, the field of organic photovoltaics has been developed rapidly, particularly, with reports of the high performance non fullerene acceptor Y6 with the donor polymer PM6. In this thesis a simple yet effective approach is demonstrated that can increase the power conversion efficiency (PCE) of a device based on PM6:Y6. By adding small amounts of betulin copolymer to the PM6:Y6 system the PCE of solar cells increase and studies are done to see what amount of betulin copolymer shows best result. Devices were characterized with paios and the film morphology was analyzed with an atomic force microscopy (AFM). Characterization of devices showed that the system consisting of 0.5 % betulin copolymer reached the highest PCE with an average PCE of 12.2 %. This approach should have a wide applicability and can be used in other organic photovoltaic systems.