Emerging Semiconductor Materials for Direct Photoelectochemical Water Splitting

High-efficiency solar-to-fuel energy conversion can be achieved using direct semiconductor-liquid junctions in a photoelectrochemical (PEC) device consisting of an n-type photoanode in tandem with a p-type photocathode. However, the development of high-performance, stable and inexpensive photoelectrodes are needed to make PEC devices economically viable. In this presentation an overview and the state-of-the-art of this technology including economic considerations is given. In addition, our group’s progress in the development of economically-prepared, high performance photoelectrodes will be discussed along with the application toward overall PEC water splitting tandem cells. Specifically, how the use of scalable solution-processing techniques (e.g. colloidal processing of nanoparticles or sol-gels) leads to limitations in charge transport and charge transfer in the resulting thin-film photoelectrode will be examined. Strategies to overcome these limitations such as using charge extraction buffer layers, catalysts, annealing/doping and nanoparticle self-assembly will be additionally presented. Materials of interest are delafossite CuFeO₂, CZTS, CIGS, CdS, organic (conjugated) semiconductors and 2D-layered MoS₂ and WSe₂.