Developing effective renewable energy sources is essential due to the world's efforts for carbon-neutrality. Organic photovoltaics (OPV) provide unique possibilities. They are much cheaper than silicon cells and moreover, can be deposited on flexible substrates, which opens the potential for new niches such as wearable electronics and building incorporated panels.
Although promising, OPV suffers from relatively low efficiencies (c.a. 5-7%) which is currently the main obstacle in the way for commercialization. The two major reasons behind this behavior are short exciton diffusion lengths and very low carrier mobility in an active layer.
Here, we present organic solar cell structures with P3HT:PC61BM mixture in weight ratio 1:0.6 as an active layer. P3HT (Poly(3-hexylthiophene-2,5-diyl)) is a conductive polymer with absorption edge in the visible region working as an electron donor. PC61BM is a C60 fullerene derivative working as an acceptor. During research, we focus on the optimization of the deposition parameters, i.e. the active layer annealing temperature, spin coating rotation speed and used solvents. Also, to test our method at a larger scale we prepare the cells onto indium-tin oxide substrates with two, substantially different sizes: 3 cm2 and 25 cm2.
As the result, we present absorption spectra of the P3HT and PC61BM. Regarding solar cells, I-V characteristics, photocurrent and external quantum efficiency measurements will be discussed.