Role of buffer in organic solar cells using C60 as an acceptor

A thin buffer layer is indispensable for a high power conversion efficiency in an organic solar cell with fullerene (C-60) as the acceptor. In present work, the authors proposed that the role of the buffer layer in an organic solar cell is to prohibit the electron transfer from metal to C-60, and thus a desired built-in electric field can promote the free carrier collection. The built-in electric field in different organic solar cells with and without the thin C-60 layer was studied by the transient photovoltage technique. The experimental results supported our proposal and indicated that the exciton blocking effect reported in the literature might not be the role of the buffer layer. (c) 2007 American Institute of Physics.