Abstract
The bandgap tunability and low-temperature processing make halide perovskites excellent candidates for achieving efficient and cost-effective tandem devices for solar cells and solar-driven water electrolysis devices. Here, we report our progress on fabricating perovskite/perovskite tandem cells consisting of two solution-processed perovskite subcells for unassisted water-splitting applications. The perovskite/perovskite tandem photoelectrodes are achieved by monolithically integrating a wide-bandgap (1.7 – 2.1 eV) Pb-based mixed-halide (Br-I) perovskite top subcell and a narrower-bandgap (1.25 - 1.55 eV) bottom subcell based on Pb-based or mixed Pb-Sn iodide perovskites. Varying the halide perovskite composition for each subcell enables us to tailor the photovoltaic performance of the tandem devices. We demonstrate that perovskite/perovskite tandem solar cells can deliver open-circuit voltages of more than 2 V. The high photovoltage provides a sufficient overpotential to drive unassisted photoelectrochemical (PEC) water splitting with a solar-to-hydrogen conversion efficiency of more than 15%. After applying water-impermeable encapsulants, the perovskite/perovskite photoelectrodes can successfully operate in an aqueous environment and enable a long operational lifetime.
Published Version
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