Aggregation Structure and Conversion Efficiency in Organic Solar Cell Utilizing Surface Plasmon Excitation

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Short-circuit photocurrents (Isc) due to surface plasmon excitations have been investigated for the organic solar cells using Langmuir-Blodgett (LB) films of merocyanine (MC) and squarylium (SQ) dyes. Tie MC and SQ dyes exhibit p-type conduction, and the Schottky and Ohmic contacts are obtained at the interfaces between the dye LB films and Al thin films and between the dye LB films and Ag thin films, respectively. Since die Schottky diodes show the photoelectric effects, the Schottky photoelectric cells have been constructed The organic solar cells with two kinds of structures, that is, prism/Al thin film/dye LB film/Ag thin film (type I) and prism/MgF_2, thin film/Al thin film/dye LB film/Ag thin film (type II), have been prepared, In the attenuated total reflection (ATR) method, the types I and II have the Kretschmann and both the Kretsclimann and Otto configurations, respectively. Surface plasmons have been resonantly excited at the interface between Ag thin film and air for the ty … More pe I and at the interfaces between MgF_2, thin film and Al thin film and between Ag thin film and air for die type II. The ATR and I_<sc> properties have been simultaneously measured as a function of the incident angles of the laser beams. The peaks of I_<sc> have corresponded to the resonant angles of the ATR curves. The electric fields and optical absorptions in the cells, have been also calculated using the dielectric constants and the film thicknesses obtained from die ATR measurements. The calculated absorptions in the dye LB layers as a function of the incident angles have corresponded to the results of I_<sc>. It has been estimated that the I_<sc> for both types I and II could be enhanced by the excitations of surface plasmons in the ATR configurations. The enhancement of I_<sc> due to SP excitations and the conversion efficiency of organic solar cells were thought to be related to the aggregation structure of dye molecules. This is a great advantage for developing solar cells, sensing devices, light switches and so on. Less