Photovoltaic cells of fullerene / poly-phenylenevinylene derivative prepared by spray deposition

The spray deposition method¹) has been developed as a new way of polymer ultra-thin film preparation for organic optoelectronic devices such as an organic photovoltaic cell (OPC). In this method, a highly diluted solution of an organic material is nebulized into air and concentrated under a controlled evaporation condition. The resulting aerosol is transported by a carrier gas and deposited onto a solid substrate. This method has substantial advantages that an almost insoluble and non-evaporative material can be fabricated into a thin film, and that a separate area coating and layer-by-layer structure of polymer materials can be preformed. An OPC was prepared from highly diluted THF solutions (below 1 ppm) of fullerene / poly-phenylenevinylene (PPV) derivative mixture. The device configulation, ITO / PEDOT-PSS / fullerene-PPV / LiF / Al, is known as a bulk hetero-junction PC. By control of temperature, we obtained homogeneous active layer by spray deposition. In addition, we can achieve power conversion efficiency of 0.63% using the active layer consist of fullerene: PPV(1:1). This method has significant potential to provide a structural control of the active layer and to reduce the cost of the OPCs drastically in spite that the power conversion efficiency is slightly lower than a PC prepared in same ratio by spin-coating.