An Organic Semiconductor PEC Tandem Cell for Solar Water Splitting

© 2022 EPFL

© 2022 EPFL

LIMNO reports major advance in the photoelectrochemical (PEC) splitting of water into H2 and O2 using organic semiconductors.

The global-scale production of solar-fuels is urgently needed to progress towards a low-carbon energy economy. Solar-driven green hydrogen (H2) production via water splitting stands out as a promising approach, and using photoelectrochemical (PEC) systems can potentially realize green H2 in an economically competitive and scalable manner. PEC cells employing organic semiconductors (OS) are promising considering their compostion from widely availible carbon-based components, but despite encouraging advances with the half reactions, complete overall water splitting has remained a challenge. In a new report from LIMNO published in Advanced Energy Materials, we describe two advances we made with the organic semiconductor photocathode (semiconductor tuning and employing a self-assembled monolayer modified substrate) to afford robust photocathode operation under alkaline pH. These advances allowed the first demonstration of unassisted solar water splitting with a photoelectrochemical tandem cell employing organic semiconductors. The large-area (2.4 cm2) tandem cell had a predicted solar-to-hydrogen (STH) conversion efficiency of 0.8 %, and under unassisted two-electrode operation (1 Sun illumination) a stabilized photocurrent of 0.6 mA and an STH of 0.3 % was observed together with near unity Faradaic efficiency of H2 and O2. Our demonstration is a first step to validate the OS-based PEC tandem cell and further research will advance this technology toward practical application.


Swiss National Science Foundation (project number 200020_185041)


Zhang, D.; Cho, H.; Yum, J.; Mensi, M.; Sivula, K. An Organic Semiconductor Photoelectrochemical Tandem Cell for Solar Water Splitting. Advanced Energy Materials 2022, 2202363.