Lead-free, stable, and effective double FA4GeIISbIIICl12 perovskite for photovoltaic applications

Organic-inorganic hybrid lead halide perovskite solar cells emerge as a breakthrough photovoltaic technology with high power conversion efficiency. However, some inherent shortcomings impede their further industrialization: 1) the toxicity of Pb, 2) unstable, sensitive to moisture and/or light. To circumvent these issues, we study the lead-free and solution-processed photovoltaic devices based on the double-metals < 111 > -oriented 2D layered formamidinium germanium-antimony halide perovskites (FA(4)Ge(II)Sb(III)Cl(12)) in this contribution. Compared with benchmark MAPbI(3), the larger formamidinium is selected to replace methylammonium to form a more stable crystal structure while the double metals germanium-antimony (Ge-II-Sb-III) are chosen to replace Pb under the considerations that expanding the possible metal combinations in the design of new perovskite with analogous photovoltaic performance. The FA(4)Ge(II)Sb(III)Cl(12) perovskite behaves as a stable and efficient semiconductor with direct bandgap of similar to 1.3 eV and its conductivity is one order of magnitude higher than that of MAPbI(3). Meanwhile, FA(4)Ge(II)Sb(III)Cl(12) based solar cell with power conversion efficiency up to 4.7% can be achieved without use of any additives. This approach opens up new possibilities of exploiting lead-free perovskite that incorporates metals in different valence states and offers great potential application in photoelectric field.