B. Korgel
University of Texas at Austin,
United States
Summary:
Nanomaterials offer a variety of unique and useful properties for energy applications. This presentation will highlight a few recent research results from the group in solar cell, battery and hydrogen fuel cell applications. For solar cells, we have developed a scalable synthesis of colloidal quantum dots of copper-aluminum-zinc-sulfide (CAZS) that absorb UV light, with Stokes-shifted blue photoluminescence (PL) with quantum yields greater than 50%. These nanocrystals are being explored as down-converting protective optical films for silicon solar cells. In another solar cell application, we have been fabricating perovskite photovoltaic devices (PVs) on plastic substrates of polyethylene terephthalate (PET) embossed with micrometer-scale grooves. Electron and hole transport layers are deposited on the walls of the microgrooves, which are then filled with metal halide perovskite as the light-absorber. These microgroove solar cells are electrically connected in series to generate a high open circuit voltage (Voc>300 V). We have screened a wide range of perovskite formulations and found that cesium formamidinium lead halide (Cs0.1FA0.9PbI2.85Br0.15) provides the most stable and highest performance of the various mixed cation and anion metal halide perovskite materials. To move beyond lithium-ion batteries, we have been exploring conversion–alloying metal sulfide nanowires as electrode materials for potassium-ion batteries (PIBs). Specifically, Sb2S3 possesses high gravimetric and volumetric capacities with low redox potentials for PIBs; however, their stability is limited due to sulfur dissolution in organic electrolyte. We have developed a solid polymer electrolyte formulation that significantly improves battery stability and performance and prevents loss of sulfur from the electrode. For hydrogen fuel cell applications, we developed manganese-oxide-decorated two-dimensional silicon (Si) nanosheets (MnOₓ@SiNS) as a membrane reinforcement to Nafion NR211 that suppresses hydrogen crossover and stabilizes open-circuit voltage performance. Polymer–electrolyte membrane fuel cells (PEMFCs) suffer chemical degradation driven by peroxide-derived radicals and mixed-potential chemistry in the membrane, which are exacerbated by hydrogen crossover. The addition of MnOₓ@SiNS to NR211 membrane significantly improves membrane durability and performance.