All-Perovskite Tandem Photoelectrodes for Unassisted Solar Hydrogen Production

Unassisted solar water splitting
by multijunction tandem
photoelectrodes
is a sustainable approach to generating green hydrogen fuels. Here,
we report on the fabrication of monolithically integrated all-perovskite
tandem photocathodes for efficient unassisted solar water splitting.
All-perovskite tandem photocathodes wired to an iridium oxide anode
deliver a high photovoltage of more than 2 V with an operating photocurrent
density of 12.5 mA cm–2 at zero applied bias under
simulated AM1.5G 1 sun illumination, yielding a solar-to-hydrogen
(STH) conversion efficiency of 15%. The tandem photoelectrode demonstrates
continuous operation in water for more than 120 h under simulated
1 sun illumination with less than 5% efficiency loss. A technoeconomic
analysis shows the projected production cost of all-perovskite tandem
photoelectrodes is $30 m–2, promising a levelized
cost of hydrogen of less than $1/kg if sufficient device longevity
is realized. This work provides a path toward achieving cost-effective
unassisted solar hydrogen fuel production.