Enhancement of optical absorption and photocurrents in solar cells of merocyanine Langmuir-Blodgett films utilizing surface plasmon excitations

Short-circuit photocurrents (I-SC) due to surface plasmon (SP) excitations were investigated for the solar cells using Langmuir-Blodgett (LB) films of merocyanine (MC) dye molecules. The Schottky photoelectric devices with two kinds of structures, that is, prism/Al/MC LB film/Ag (type A) and prism/MgF2/AlMC LB film/Ag (type B) were prepared. Type A has the Kretschmann configuration and type B has both the Kretschmann and the Otto configurations. In the attenuated total reflection (ATR) measurements, SPs were resonantly excited at the interface between Ag and air for type A and at the interfaces between MgF2 and Al and between Ag and air for type B. The ATR and I-SC properties were simultaneously measured as a function of the incident angles of the laser beams. The peaks of I-SC corresponded to the resonant angles of the ATR curves. The electric fields and optical absorption in the cells were also estimated. The calculated absorption in the MC layers as a function of the incident angles corresponded to the I-SC curves. The optical absorption in the MC layers turns out to be correlated directly to the profiles of I-SC. It was estimated that I-SC could be enhanced by the excitations of SPs in the ATR configurations. (C) 2002 Elsevier Science B.V. All rights reserved.