Functional microprism substrate for organic solar cells

Abstract

A novel cell architecture for organic solar cells is presented which is based on a functional microprism substrate. In contrast to the most widely used planar cell architecture with a transparent indium tin oxide (ITO) electrode, the microstructure results in a folded solar cell. Of benefit are the light trapping effect and the substitution of the ITO-electrode by a highly conductive polymer layer with a supporting metal grid. Optical simulations were performed and reveal a gain in absorption in the photoactive layer due to the inclined incidence of radiation and due to the second reflection. Optimal dimensions of the microstructure were calculated by taking the sheet resistivity of the polymer anode and the shading effect of the metal grid into account. The metal grid with a low effective sheet resistance below 1 Ω/□ was realised by evaporation techniques using the microstructure as a self aligning mask. Investigations on the thin film formation are presented. First microprism solar cells with solar efficiencies comparable to planar ITO-reference solar cells were realised.