High efficiency tandem organic photovoltaics incorporating small molecule blended squaraine donors and a fullerene acceptor

We demonstrate a high efficiency organic tandem cell based on a pair of sub-cells employing solution and vapor deposited donors and a fullerene acceptor. One sub-cell that absorbs primarily from the green into the near infrared consists of a solution-processed, solvent-vapor-annealed blended squaraine/C₇₀ bilayer heterojunction, while the second, visible absorbing sub-cell consists of a vapor-deposited tetraphenyldibenzoperiflanthene (DBP):C₇₀ planar-mixed heterojunction. The resulting stacked tandem device harvests photons of λ <; 800 nm while providing an open-circuit voltage (V_OC) of 1.83 V and η_p = 7.8 ± 0.4 %.