Efficient light harvesting with LB films for application in crystalline silicon solar cells

摘要

The term light harvesting is used in photosynthesis as a natural method to significantly increase the absorption cross section of the reaction centre via excitation energy transfer. In application to crystalline silicon solar cells, light harvesting offers the potential for dramatic cost reduction by combining the advantages of high optical absorption of dye molecules with the efficient electronic properties of crystalline silicon. We have carried out fluorescence lifetime measurements using time correlated single photon counting for cyanine LB dye monolayers near the silicon surface. The measurements have been carried out for both <100> and <111> crystal orientations of the silicon surface, showing the dependence of energy transfer rate as a function of the separation between the dye layer and silicon. We find that the fluorescence lifetime of the dye monolayer is significantly shortened when close to the silicon surface indicating efficient energy transfer. The dissipation of the excitation energy near silicon is explained using a classical theory for quenching of molecular fluorescence near metals.