Mixed-Organic-Cation Perovskite Photovoltaics for Enhanced Solar-Light Harvesting

Hybrid organic-inorganic lead halide perovskite APbX(3) pigments, such as methylammonium lead iodide, have recently emerged as excellent light harvesters in solid-state mesoscopic solar cells. An important target for the further improvement of the performance of perovskite-based photovoltaics is to extend their optical-absorption onset further into the red to enhance solar-light harvesting. Herein, we show that this goal can be reached by using a mixture of formamidinium (HN=CHNH3+, FA) and methylammonium (CH3NH3+, MA) cations in the Aposition of the APbI(3) perovskite structure. This combination leads to an enhanced short-circuit current and thus superior devices to those based on only CH3NH3+. This concept has not been applied previously in perovskite-based solar cells. It shows great potential as a versatile tool to tune the structural, electrical, and optoelectronic properties of the light-harvesting materials.