Conducting Polymer Photoelectrodes—Design Criteria, Interface-to-Interphase Considerations and Durability

Creating organic semiconductor-based photoelectrodes is not as simple as interfacing optimized organic photovoltaic materials with an electrolyte. In photoelectrodes, charge extraction occurs through the generation of molecular fuels from sunlight (i.e. hydrogen), which are either kinetically limited or mass transport limited. Durable and high performing organic photoelectrodes require balancing the photojunction properties with charge transport, attention to catalytic attachment, and a strong emphasis on mitigating parasitic chemical reactions and resistances.<br/><br/>This talk will consider the implementation and feasibility of highly scalable, π-conjugated polymer materials in photocathodes. Why conducting polymers? The mixed electrical-ionic transport properties present a complex polymer/electrolyte interphase that if understood, could provide control over local environments afforded through synthesis, long-lived charge carrier lifetimes, and flexible, low-cost, and scalable thin film formats which circumvent the shortcomings of inorganic materials (surface states, grain boundaries, challenges in processing, and mechanically unstable platforms).<br/><br/>The realization of all-organic semiconductor systems that capture light energy and convert it into chemical energy requires a detailed understanding of structure-property relationships governing the interconnected dynamics of photo-generation, transport, and electron transfer across multiple interfaces. Dark electrochemical processes must be understood before increasing the complexity via light-matter interactions. The Center for <u>S</u>oft <u>P</u>hoto<u>E</u>lectro<u>C</u>hemical <u>S</u>ystems (SPECS) is an Energy Frontier Research Center focused on the basic science questions that underpin the development of low-cost, robust energy conversion and energy storage technologies based on new organic polymer (plastic) electronic materials. These materials are predicted to fill a critical position in the U.S. energy portfolio, providing for next-generation fuel-forming platforms (energy conversion) and batteries (energy storage) that cannot currently be achieved with conventional (hard) inorganic materials. This talk will focus on increasing complex, multiple interface platforms, towards the goal of photons-to-electrons-to-molecules energy conversion processes for all-polymer photocathodes. A number of emerging <i>in situ/operando</i> spectroelectrochemical and scanning electrochemical cell microscopy approaches will be discussed for this exciting new area of energy conversion.