Organic tandem solar cells with complementary absorbing layers and a high open-circuit voltage

Tandem organic solar cells with peak conversion efficiencies (eta) of 5.15% are demonstrated. This is achieved by stacking two different planar heterojunction devices, each with a high open-circuit voltage (V(oc)). The phthalocyanine based donor materials in the employed subcells possess complementary absorption, a quality of critical importance to optimize photocurrent in a series connected tandem cell. The tandem structure produces V(oc) values of nearly 2 V, while fill factor remains above 60%. The measured eta corresponds to a 40% increase compared to eta of the optimal single cells. (C) 2010 American Institute of Physics. [doi:10.1063/1.3464169]