Film structures and electro-optic properties of multilayer organic thin film semiconductors

The performance of organic photovoltaic cells containing tin-phthalocyanine (SnPc) as a donor layer and fullerene (C(70)) as an acceptor layer is studied using multi layer structures incorporating two hetero junctions with an ultra thin layer of Ag as an internal electrode. The photovoltaic conversion efficiency of the indium-tin oxide (ITO)/poly (3,4-ethylene dioxythiophene): poly (styrene sulfuric acid) (PEDOT:PSS)/SnPc/SnPc:C(70)/C(70)/Ag/SnPc/SnPc:C(70)/C(70)/Ag cell is improved from 1.54 to 1.90% by heating the substrate at 100 degrees C during film evaporation. X-ray diffraction measurements indicate that the ordering of phthalocyanine molecules is improved from the a phase to the phase by heating the substrate.