Exploiting Disordered Photonics for Light Trapping in Photoelectrochemical Energy Conversion Applications
by Coridan, Robert H.
Photoelectrochem. (PEC) solar energy conversion applications rely on chem. reactions driven by photogenerated minority carriers (electrons or holes) at a semiconductor-liquid interface. The optical, electronic, and chem. transport processes characteristic of these PEC reactions operate on independent and generally disparate length scales. Fabricating electrodes with hierarchical structure can optimize the performance for each of these processes simultaneously. We have recently introduced an approach to synthesizing disordered colloidal composites (SiO2 and polystyrene) and selectively removing organic components from the structure. We can functionalize these structures with a thin semiconductor light absorber to improve the rate of PEC water oxidation, for example. This approach can also generate the multiscale structure necessary for uniting the many important transport length scales for PEC energy conversion into a single, simple material. In this talk, we will introduce our combined theor. and exptl. approach to building photoelectrodes based on disordered photonic scaffolds as a way to dramatically improve light absorption and quantum yield in thin-film semiconductors. One significant issue is that disordered materials can only be defined by ensemble or statistical parameters (pore diameter, scatterer diameter, relative volume fractions) rather than as precise structures. This results in a true variance intrinsic to the ensemble structure. Simulations of the ensemble properties require a large number of examples for a given configuration to understand this variance, which comes with a high computational cost. We will describe our recent efforts to use machine learning to improve the computational efficiency of finite-difference time-domain simulations in ensembles of disordered photonic glasses. We will outline how these algorithmic predictions can be used to identify the most efficient ensemble configuration for a given semiconductor photoelectrode. Finally, we will discuss recent exptl. photoelectrode constructions synthesized via at. layer deposition and electrodeposition. We will conclude by considering methods to selectively functionalize the high-quality light-trapping defects via photoelectrodeposition.