Interfacial connections between organic perovskite/n+ silicon/catalyst that allow integration of solar cell and catalyst for hydrogen evolution from water

The rapidly increasing solar conversion efficiency (PCE) of hybrid organic-inorganic perovskite (HOIP) thin-film semiconductors has triggered interest in their use for direct solar-driven water splitting to produce hydrogen. However, application of these low-cost, electronic-structure-tunable HOIP tandem photoabsorbers has been hindered by the instability of the photovoltaic-catalyst-electrolyte (PV+E) interfaces. Here, photolytic water splitting is demonstrated using an integrated configuration consisting of an HOIP/n+silicon single junction photoabsorber and a platinum (Pt) thin film catalyst. An extended electrochemical (EC) lifetime in alkaline media is achieved using titanium nitride (TiN) on both sides of the Si support to eliminate formation of insulating silicon oxide, and as an effective diffusion barrier to allow high-temperature annealing of the catalyst/TiO2-protected-n+silicon interface necessary to retard electrolytic corrosion. Halide composition was examined in the (Cs1-xFAx)PbI3 system with a bandgap suitable for tandem operation. A fill factor (FF) of 72.5% was achieved using a Spiro-OMeTAD-hole-transport-layer (HTL)-based HOIP/n+Si solar cell, and a high photocurrent density of -15.9 mA/cm2 (at 0V vs reversible hydrogen electrode) was attained for the HOIP/n+Si/Pt photocathode in 1M NaOH under simulated one-sun illumination. While this thin-film design creates stable interfaces, the intrinsic photo- and electro-degradation of the HOIP photoabsorber remains the main obstacle for future HOIP/Si tandem PEC devices.