Spray-deposited PEDOT:PSS for inverted organic solar cells

The method of spray-depositing PEDOT:PSS allows the fabrication of thin films with controlled thickness on polymer layers. PEDOT:PSS is used in inverted ITO/TiO2/P3HT:PCBM/PEDOT:PSS/Ag solar cells to optimize the work function of the hole-collecting electrode. The interlayer is also found to protect the organic layer during metal top deposition and improve the contact between P3HT–PCBM and the Ag electrode, which is confirmed using two different metal-deposition techniques; thermal evaporation and sputtering. Cells with PEDOT:PSS show full VOC and efficiency immediately after fabrication, whereas devices without PEDOT:PSS exhibit low performance in the beginning and improve significantly during the first 10 days after production. Devices are long-term stable if stored in the dark and in ambient air and show no significant performance decrease after 80 days. No inert nitrogen atmosphere is needed for any fabrication step, thus reducing the potential production costs since no glove box has to be used.