Life Cycle Assessment Studies in Perovskite Solar Cells
Perovskite Solar Cells (PSCs) have significantly advanced since they were first proposed as a novel and promising Photovoltaic (PV) technology designed to deliver photoconversion efficiencies higher than traditional PV systems. PSCs have taken the lead among the most recent photovoltaics due to their exceptional versatility, the ability to tune the energy band gap, and the ability to create tandem solar devices with other PV technologies, such as silicon-based solar cells and Copper Indium Gallium Selenide (CIGS) solar cells. By achieving a photoconversion efficiency of over 25%, they recently set a new laboratory record with this figure surpassing that of thin-film PVs, as well as establishing a benchmark set formally by multi-crystalline silicon solar cells.
PSC PV technologies have the potential to provide a significant amount of energy and reduce the reliance on fossil fuels for the generation of electricity whilst reducing greenhouse gas emissions. Their low manufacturing costs, high photoelectric conversion efficiency, low-quality requirements of raw materials, simple manufacturing processes and low energy consumption are highly advantageous. However, their poor structural stability, difficulty in deploying Perovskite Solar Cells technology over large areas, and environmental problems have limited the proliferation of this technology. Furthermore, there is an increased uncertainty about whether this technology has a more significant life cycle environmental footprint than contemporary PV systems, even though the photoelectric conversion efficiency is typically larger. The outlined research projects aim to provide details regarding the life cycle analysis of PSC systems and determine whether such systems offer a reduced environmental footprint overall.
Perovskite Solar Cells – Lifecycle Assessment Studies
Researchers in the Department of Civil and Environmental Engineering, South Dakota School of Mines and Technology, USA, performed a life cycle assessment for 13 PSC recycling techniques focusing on the recovery of coated glass. They found that ecotoxicity due to the consumption of materials was the major contributor to the environmental impact of PSCs, with all but one of the techniques generating more environmental impact than the production of virgin-coated glass and also found that material reuse and recovery were key to sustainable coated glass recycling.
Recovering the solvent could decrease the impact of these techniques by 56-68%, with the potential for additional reductions by reusing these solvents. Furthermore, thermal or physical process techniques would require lower electricity and material use and reductions in solvent reuse and recovery to become an environmentally sustainable reality compared with traditional PV technologies.
Researchers in the Department of Chemical and Biological Engineering at Northwestern University, USA, performed a life cycle assessment for two types of solution-processed Perovskite Solar Cells modules to understand the overall environmental impact of this promising PV class. We equipped one module with Fluorine-doped Tin Oxide (FTO) glass, a gold cathode, and a mesoporous TiO2 scaffold. We equipped the other module with Indium Tin Oxide (ITO) glass, a silver cathode, and an O thin film. They developed comprehensive life cycle inventories for all components used in these modules.
Environmental Impact Assessment and Comparisons
The researchers conducted life cycle impact assessments for 16 common life cycle impact indicators (Eco-indicator 99 method) and two sustainable indicators:
1.) the Energy Payback Time (EPBT), and
2.) the CO2 emission factor.
They compared the results of the Eco-indicator 99 method, the EPBT, and the CO2 emission factor among existing PV technologies and performed an uncertainty analysis and sensitivity analysis for the two modules. The results demonstrated that PSC modules possess the shortest EPBT overall, with future research required to improve the system performance ratio and the device lifetime. Furthermore, it was suggested that reducing precious metal consumption and energy-intensive operations would reduce the CO2 emissions factor of PSCs and make them similar in environmental impact to traditional PV systems.
Perovskite Solar Cells: Environmental Impact and Future Potential
To understand the potential environmental impact of Perovskite Solar Cells PV devices and thus analyse the future potential of PSCs, a cradle-to-gate life cycle assessment was conducted on a 3-cell PSC module with an active area of 24.6cm2 in the Engineering Department at the University of Porto, Portugal. We prepared the device under investigation using an optimized fabrication process at LEPABE – the Laboratory for Process Engineering, Environment, Biotechnology, and Energy. We undertook the life cycle analysis using data from the Life Cycle Inventory database (Ecoinvent v3.5) and the surrounding literature.
The results showed that material and direct energy usage involved in PSC production contributed to the highest negative environmental impacts. The back-contact layer made of gold was the main source of environmental impact since it contributed to more than 60% of the life cycle impact in every impact category and constituted the main PSC carbon footprint contributor. Researchers revealed that the fabrication of the mesoporous layer contributed 73.9% to the overall life cycle impact of perovskite production, making it the most energy-consuming step compared to the manufacturing steps of other layers.
Concerning only the material class, FTO glass was the compound that appeared to have the most impact on the environment, apart from gold. The electron transporting layer, mainly due to acetylacetone, also showed some relevance towards climate change. Researchers at the Chalmers University of Technology, Sweden, undertook a life cycle assessment of a PSC and an equivalent comparison to the most commonly used silicon solar cell. Several parameters were varied in the study to determine which processes contribute the most to the environment. The study found that PSCs could be competitive with silicon Perovskite solar cells from an environmental point of view if produced on a large scale. Management of lead use and emissions during the production process of PSCs had the largest impact on the results.
If we assume that all of the lead used was supplied from recycling, and we completely prevented emissions of lead from the cell itself during and after the use phase, PSCs demonstrated better environmental performance than traditional silicon cells. Regarding manufacturing technology, the study also showed that the blade coating technology was environmentally preferable over spin coating for large-scale production of PSCs.
Perovskite-Silicon Tandem Modules: Environmental Impact and Sustainability
German researchers at the Fraunhofer Institute for Solar Energy Systems, alongside Oxford PV, UK, have examined the life cycle of perovskite-silicon tandems to investigate how this novel technology might impact the sustainability of the energy supply and solar production in general. In this study, Oxford PV, which is currently ramping up commercial production of PSC modules in Germany, is the primary source of materials and manufacturing processes. It is the first to examine the effects of perovskite technology on the environment using data from actual industrial production.
The fabrication of tandem cells begins with the processing of silicon Perovskite solar cells, followed by the addition of an active cell layer. Naturally, the environmental impact grows as there is more manufacturing involved. The researchers discovered that the extra energy needed to create a tandem module might be more than compensated for by the extra energy it will generate over its lifetime. When the researchers accounted for the extra energy produced over the tandem module’s 25-year lifetime, they discovered that the perovskite-on-silicon module had between 6% and 18% less impact on the environment than an equivalent silicon module.
The Future of Perovskite Solar Cells
The market size for PSCs was estimated at US$414 million in 2022 and is projected to grow at a Compound Annual Growth Rate (CAGR) of 12.2% from 2022 to 2027, totalling US$825 million. In general, life cycle analysis studies of PSC modules indicate that additional environmental impacts during manufacturing are more than offset by the higher energy yield over their lifetime.
The development of perovskites has made impressive and encouraging overall progress. Perovskites have developed efficiencies on par with the more established Cadmium Telluride (CdTe) systems in just a few years. With perovskites, high performance can be attained relatively easily, which is advantageous. Furthermore, the development of perovskites has advanced at a rate that has been between 100 and 1,000 times faster than that of CdTe systems when comparing the amount of time spent on research to achieve a 1% increase in efficiency in conventional PV cells.