To achieve net-zero greenhouse gas emissions by 2050 and limit the global average temperature rise to below 1.5 degrees Celsius, it is essential to increase the utilization rate of renewable energy, especially solar photovoltaic energy.
Currently, greenhouse gas emissions from industries such as power generation, heating, and transportation account for approximately 75% of global emissions. Therefore, the international community must seize every opportunity to accelerate the replacement of existing fossil fuels with renewable energy, while simultaneously installing carbon-neutral energy sources to meet the growing energy demands of developing countries. The International Renewable Energy Agency (IRENA) has proposed a vision for a fundamentally transformative global energy system, proposing that by 2050, 90% of the world's projected 30 terawatts of electricity demand will be provided by renewable energy, with solar photovoltaic (PV) and onshore/offshore wind power accounting for 14 terawatts and 8 terawatts, respectively.
While other international organizations have proposed alternative plans, such as the World Energy Outlook, there is a clear consensus that rebuilding the global energy economy is a major challenge that requires a great deal of technological and policy coordination, and the path forward will heavily depend on utilizing the world’s most abundant energy source: sunlight.
To fully utilize solar energy, scientists have been working to maximize the conversion of light energy into electrical energy. Currently, ground-based photovoltaic systems largely use silicon-based solar cells, with a photoelectric conversion efficiency of up to 26%. A recent study published in *Applied Physics Letters* by researchers from Oxford PV has paired perovskite with silicon to produce a more powerful solar cell that can convert up to 29.52% of light energy into electrical energy, breaking through the conversion efficiency limitations of traditional silicon solar cells.
After decades of development, thanks to the joint efforts of research institutions and the solar photovoltaic industry, the price of photovoltaic modules has decreased exponentially. In the past decade alone, the cost of photovoltaic power generation has dropped by more than 85%, making solar energy cheaper than fossil fuel resources in most parts of the world.
This has significantly reduced costs, and coupled with forward-looking energy policies implemented by many countries, solar photovoltaic (PV) has become an ideal and affordable clean energy source for the power generation and transportation sectors. However, as of 2020, the global cumulative installed PV capacity was only 0.7 terawatts, meaning that significant growth in PV production and installation is needed to achieve IRENA's 2050 solar energy targets. Currently, the dominant solar PV technology is based on crystalline silicon (c-Si), accounting for 95% of production in 2019, and the cost of silicon PV is expected to continue to decline. Currently, the dominant solar PV technology is based on crystalline silicon (similar to monocrystalline silicon), accounting for 95% of production.
To further reduce energy costs, disruptive innovation is needed to surpass it. A technologically proven strategy to improve the efficiency of c-Si modules is to pair them with another, wider-bandgap solar material that can selectively absorb higher energy regions of the solar spectrum.
Researchers say that by stacking this material on top of lower bandgap c-Si, a tandem structure can be achieved, overcoming the fundamental Shockley-Quiselle limit of single-junction devices. This strategy has been identified in the International Technology Roadmap for Photovoltaics (ITRPV), which predicts that silicon-based tandem cells will enter the photovoltaic market in 10 years. While several options exist for pairing wide-bandgap top cells with c-Si, metal halide perovskites are a promising candidate, having been the subject of intensive research and development over the past decade.
Researchers believe that the pairing of perovskite and c-Si in tandem devices is ideal at many different key levels, representing a faster pathway for tandem PV to successfully enter the terrestrial energy market. From this perspective, we will discuss how perovskite and silicon are well-matched for tandem photovoltaic power generation from key angles of materials science, manufacturing, sustainability, and business, and how their combination represents a technological shift that will help accelerate global photovoltaic capacity growth and mitigate climate change.
