Evaluation of exciton diffusion length in highly oriented fullerene films of fullerene/p-Si(100) hybrid solar cells

Highly oriented fullerene (C60) films on p-Si (100) substrates were fabricated to evaluate the crystallinity dependent exciton diffusion length of C60 (LC60). The crystal structure of the C60 films was examined using grazing incidence X-ray diffraction. The results of an in-plane rocking scan and a pole figure suggested that a 12-fold-symmetry crystal was grown with the C60(111) surface interfaced to the Si(100) substrate. The photovoltaic characteristics of the oriented C60/p-Si(100) hybrid solar cells were evaluated. A masking effect was clearly evident in the incident photon-to-current conversion efficiency (IPCE) spectra. LC60 was evaluated using both experimental IPCE spectra and that produced by one-dimensional-optical simulation. It was concluded that LC60 for highly oriented C60 was 60 nm, which was longer than that of disordered C60 films.