Anneal effect of Joule-heating on P3HT:PCBM-based organic thin-film photovoltaic cell

It is well-known that the bulk-hetero-type photovoltaic cells consisting of Poly(3-hexylthiophene-2,5-diyl) (P3HT) and (6,6)-phenyl-C61 butyric acid methyl ester (PCBM) depend on the annealing process of temperature, cooling rate, etc. Usually the annealing is carried out in a laboratory by putting on a hot-plate and keeping in a hot oven. However, since a photovoltaic cell is a device that needs the area, its substrate size will enlarge in future. The increase in substrate size leads to the growing in size of baking devices. Therefore, we propose the new anneal method based on Joule-heating of transparent electrode, indium-tin-oxide (ITO). The annealing method due to Joule-heating shows faster response of temperature than the other because of a small heat reservoir. We compare the device using Joule-heating with the device using a hot-plate. The device structure is ITO/PEDOT:PSS/P3HT:PCBM/LiF/Al. The anneal temperature and time are 140°C and 10 min. The cooling time from 140°C to RT of Joule-heating and hot-plate is 5 min. The devices annealing by using hot-plate and joule-heat have almost the same PCE of 2.5 % under 1 sun.