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

Short-circuit photocurrents (ISC) 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/Al/MC 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 ISC properties were simultaneously measured as a function of the incident angles of the laser beams. The peaks of ISC 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 ISC curves. The optical absorption in the MC layers turns out to be correlated directly to the profiles of ISC. It was estimated that ISC could be enhanced by the excitations of SPs in the ATR configurations.