Determining the internal quantum efficiency of highly efficient polymer solar cells through optical modeling

A power conversion efficiency of 4.2% (AM1.5, 1000 W/m(2)) is measured for an organic solar cell based on an active layer of an alternating copolymer, containing a fluorene and a benzothiadiazole unit with two neighboring thiophene rings, and a fullerene derivative. Using optical modeling, the absorption profile in the active layer of the solar cell is calculated and used to calculate the maximum short circuit current. The calculated currents are compared with measured currents from current-voltage measurements for various film thicknesses. From this the internal quantum efficiency is estimated to be 75% at the maximum for the best device. (c) 2007 American Institute of Physics.