Perovskite-kesterite monolithic tandem solar cells with high open-circuit voltage

We report a monolithic tandem photovoltaic device with earth-abundant solution processed absorbers. Kesterite Cu2ZnSn(S,Se)4 and perovskite CH3NH3PbI3 solar cells were fabricated monolithically on a single substrate without layer transfer. The resulting devices exhibited a high open circuit voltage (Voc) of 1350 mV, close to the sum of single-absorber reference cells voltages and outperforms any monolithic tandem chalcogenide device (including Cu(In,Ga)Se2) reported to date. Ongoing optimization of several device elements including the severely limiting top contact electrode is expected to yield superior currents and efficiency. Importantly, our device architecture demonstrates the compatibility and synergistic potential of two of the most promising emerging photovoltaic materials and provides a path for optimization towards >20% efficiency.