Michael Wilhelm4,Feray Ünlü1,Ashish Kulkarni2,Khan Lê1,Christoph Bohr1,Andrea Bliesener1,Seren Öz1,Ajay Jena2,Yoichi Ando1,Tsutomu Miyasaka2,Thomas Kirchartz3,Sanjay Mathur1
Universität zu Köln1,TOIN University of Yokohama2,Forschungszentrum Jülich GmbH3,University of Cologe4
Michael Wilhelm4,Feray Ünlü1,Ashish Kulkarni2,Khan Lê1,Christoph Bohr1,Andrea Bliesener1,Seren Öz1,Ajay Jena2,Yoichi Ando1,Tsutomu Miyasaka2,Thomas Kirchartz3,Sanjay Mathur1
Universität zu Köln1,TOIN University of Yokohama2,Forschungszentrum Jülich GmbH3,University of Cologe4
Lead-halide perovskites have outstanding properties and were quickly developed to have power conversion efficiencies beyond 25%. However, the toxicity of lead (Pb) hinders the commercialization of lead-based materials. Exploitation of the isoelectronic Bi<sup>3+</sup> gained interest as substitute. We investigated single and double A-site cation engineered bismuth perovskite-inspired materials for solar energy conversion. We replaced methylammonium with different organic and inorganic cations such as formamidinium, dimethylammonium, guanidinium, cesium, rubidium, potassium, sodium and lithium. In addition, mixed methylammonium/cesium bismuth iodides with different cation ratios were used as absorbers in photovoltaic devices and improved power conversion efficiencies of 1.5% were achieved. This more than 5-fold enhancement in comparison to 0.22% and 0.24% for the respective single cation materials is attributed to the band gap reduction.