Monolithically Integrated BiVO4/Si Tandem Devices Enabling Unbiased Photoelectrochemical Water Splitting

Gihun Jung, Choongman Moon, Filipe Martinho, Yonghoon Jung, Jinwoo Chu, Hyewon Park, Alireza Hajijafarassar, Rasmus Nielsen, Jørgen Schou, Jeongyoung Park, Peter Christian Kjærgaard Vesborg, Ole Hansen, Yunseog Lee, Stela Canulescu, Byungha Shin

Research output: Contribution to journalJournal articleResearchpeer-review


A photoelectrochemical (PEC) water splitting device based on a dual-junction monolithic tandem cell that utilizes NiOOH/FeOOH/BiVO4/SnO2/Ta:SnO2 (TTO)/tunnel oxide passivated contact (TOPCon) Si is reported. The PEC device achieves a maximum photocurrent density of 1.4 mA cm−2 (equal to a solar-to-hydrogen conversion efficiency of 1.72%) in 1.0 m potassium borate solution (pH 9) when illuminated with air mass 1.5 G simulated solar irradiation, which is the highest value among dual-junction monolithic photoelectrochemical cells except for III–V materials. The TOPCon Si not only works as an appropriate bottom photoelectrode for subsequent high-temperature BiVO4 processing but also offers a high photovoltage of 590 mV. Transparent and conductive TTO grown by pulsed laser deposition serves as a recombination layer to achieve effective integration. In addition, the TTO provides chemical and physical protection, allowing the surface of the TOPCon Si to exhibit 24 h of tandem cell stability under weak base electrolyte conditions. The SnO2 hole-blocking layer inserted between TTO and BiVO4 enhances the charge separation of BiVO4, allowing the device to achieve high efficiency. Artificial leaf-type monolithic tandem cells consisting of NiFe/BiVO4/SnO2/TTO/TOPCon Si/Ag/Ti/Pt with a solar-to-hydrogen efficiency of 0.44% are also demonstrated.
Original languageEnglish
Article number2301235
JournalAdvanced Energy Materials
Issue number15
Number of pages29
Publication statusPublished - 2023


  • Photoelectrochemical water splitting
  • Monolithic integration
  • Wireless tandem
  • Unassisted water splitting


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