Organic semiconductor colloids: From the knowledge acquired in photovoltaics to the generation of solar hydrogen fuel

The recent interest in the application of organic semiconductor colloids to photocatalytic hydrogen evolution has sparked the need for an assessment of the current state of this research field. Here, we showcase how the lessons learned from organic photovoltaics (OPV) research can be applied to new applications in the generation of solar fuels, such as in photocatalytic hydrogen evolution. Photovoltaics generated from organic semiconductor nanoparticles (NPs) started with a power conversion efficiency at less than 0.01% in 2003, since then the technology witnessed a steady climb to 7.5% reported in 2018. A large fraction of this technology improvement can be attributed to morphology improvement of the organic semiconductor colloids, improvements which can now be transferred to benefit the field of photocatalytic hydrogen evolution. We begin with an introduction to conjugated materials, then move to a thorough description of NP dispersion processes, comprising the miniemulsion and the nanoprecipitation methods, before moving to a summary of the different morphologies encountered in organic NPs, their impact on OPV performance and how this parameter is of crucial importance for photocatalytic hydrogen generation. Indeed, organic semiconductor colloids conveniently provide the field of photocatalytic hydrogen generation with a nanoengineering toolkit upon which to customize morphologies to increase photocatalytic activity and enhance hydrogen evolution rates (HER)