IMPORTANCE OF OPTICAL CONFINEMENT IN ORGANIC THIN FILM SOLAR CELLS

We have found that the short-circuit current, J(sc), of polymer/fullerene [RR-P3HT/C-60] solar cells has a clear dependence on the surface roughness of the ITO vertical bar glass substrate after the post-metallization annealing. We prepared an ITO surface with an average roughness, R-a, of 1 - 9 nm by chemical etching. When solar cell structures were made on these ITO surfaces, the diffuse reflection intensity increases with the increase in ITO surface roughness. Also, the solar cell performance, J(sc) increases drastically with ITO roughness after annealing. This feature suggests that the diffuse reflection of Al vertical bar P3HT/C-60 interface is quite important for optical confinement of the cells, after post-metallization annealing. The effect is quite effective to improve cell performances.