Photovoltaic Properties of Polythiophen:Fullerene Derivative Solar Cell Using Annealing due to Anode Joule Heating

Abstract

A hot-plate annealing is often used as the anneal process of a regioregular poly(3-hexylthiophene-2,5-diyl) (P3HT): [6,6]-phenyl-C₆₀-butyric acid methyl ester (PCBM) thin-film solar cell. In laboratories, the anneal procedure is carried out by putting the substrates on a hot plate. We tried to anneal the specimens using the Joule heat due to applying current to ITO electrode. The configuration of ITO electrode is 29mm-length and 2mm-width. The current flowing in ITO is from 60 to 80 mA. The temperatures corresponding to these currents are ∼ 95 and ∼140°C. The temperature change of the specimen on a hot plate can be restaged by the Joule heating. Although the photovoltaic properties of non-annealing specimen are the poorest of the three, those of Joule heat annealing specimen are the same as those of hot-plate annealing specimen. The absorption spectra of three specimens are same. The IPCE spectrum of non-annealing specimen is 70 % lower than the other specimens. This result shows the carrier transport in the active layer and the carrier ejection from the active layer to both electrodes. The Joule heat anneal is found to give the P3HT:PCBM device performance similar to the hot plate anneal.