Organic photovoltaic devices based on polythiophene films electrodeposited on FTO substrates

We investigated photovoltaic devices based on electrochemically deposited monolayer of neat polythiophene (PT) films onto fluorine-doped tin oxide (FTO)/glass substrates. The photo-electrical behavior of these devices, using FTO and aluminum as electrodes, presented symbatic and antibatic response. These devices presented Voc∼700 mV, under monochromatic irradiation (λ=610 nm; 1 W/m2) and the Incident Photon Converted to Electron Efficiency (IPCE) around 5%, with illumination through the FTO electrode (λ=610 nm; 1 W/m2). Cyclic voltammogramms and optical measurements were used to estimate the PT HOMO and LUMO energy levels, as well to demonstrate that the potential synthesis did not produce any polymer degradation. Using the Schottky model expression in the dark current voltage characteristics it was possible to obtain the barrier height value (ϕb), for the interface PT/Al. The ϕb was quite near to the difference between the aluminum work function and the PT electronic affinity and coherent with the Voc values.