(555c) Design for the Environment: Using Hotspot-Driven Research for Solar Energy Materials

Life cycle assessment (LCA) is a comprehensive approach that examines all stages of a product’s life, starting from raw material extraction (cradle) and ending when the material returns to the earth (grave). It evaluates the cumulative environmental impacts at each stage, allowing for the assessment of trade-offs in product and process selection. By considering all life cycle stages and multiple metrics, LCA helps to avoid the issue of trading one problem for another. For example, while water is often suggested as a green solvent in chemical processing to reduce toxicity, its high enthalpy of vaporization leads to increased energy consumption during distillation. This results in a net shift from a direct toxicity problem during the synthesis stage to an increased energy demand, creating an indirect toxicity impact from energy production.

Another issue with LCA used for energy applications is the limited scope of impacts considered. LCAs of solar technology have primarily focused on cumulative energy demand (CED) and carbon footprint, as the main goal of solar energy is to replace fossil fuel energy production. The objective is to ensure that the energy and carbon footprint associated with manufacturing and installing solar panels—typically reliant on fossil fuels—is offset by the energy produced and the greenhouse gas emissions avoided over the panels' lifespan (considering both energy and carbon payback time). The existing LCA methodologies for photovoltaic (PV) systems were developed for ground-mounted or rooftop installations of mature technologies. However, these methods are not well-suited for emerging technologies or for dual-use applications such as building-integrated photovoltaics.

In this presentation, we will introduce a hotspot-driven approach developed by our group to evaluate existing chemical processes and identify more sustainable manufacturing pathways. We will provide an example the iterative method we developed and its use for the synthesis of chloroaluminum phthalocyanine (ClAlPc) and for the purification of fullerene (C60). For ClAlPc, the alternative process we developed resulted in a 3% reduction in environmental impact, a 9% decrease in cost, and a 23% decrease in chemical hazards compared to the baseline process. Regarding C60, we assessed several potential greener alternatives (linseed oil, olive oil, toluene, and xylene) to replace 1,2,4-trimethyl benzene (TMB) used in current purification processes. Despite evaluating solvents that are deemed more environmentally friendly than petroleum-based options, we found toluene to be the best alternative. Using toluene instead of the baseline complexation method led to a 59% reduction in environmental impact, an 85% decrease in cost, and a 42% drop in chemical hazards. The second part of this presentation will demonstrate how LCA can be utilized to evaluate and select materials for specific applications by optimizing net environmental benefits. We will illustrate the application of net energy and cost-benefit methods for transparent organic photovoltaics in integrated building applications.