“Clean and renewable energy technologies are extremely important for carbon reduction. Solar cells that directly convert solar energy into electricity are among the most promising clean energy technologies. High power conversion efficiency solar cells is essential to generate more electric power using a limited area and this, in turn, reduces the total cost of solar power generation,” explained lead researcher Young Presidential Professor Hou Yi, who belongs to the Department of Chemical and Biomolecular Engineering at NUS and also leads a “perovskite-based multi-junction solar cell cluster” at the Singapore Solar Energy Research Institute at NUS.

“The main motivation for this study is to improve the power conversion efficiency of perovskite/organic tandem solar cells. In our latest work, we demonstrated a power conversion efficiency of 23.6% – that’s the best performance for this type of solar cell to date,” added Dr. Chen Wei, a researcher in the Department of Chemical and Biomolecular Engineering at NUS and first author of this work.

This achievement represents a significant leap from the current power conversion rate of approximately 20% reported by other studies of perovskite/organic tandem solar cells, and approaches the power conversion rate of 26.7% silicon solar cells, which is the dominant solar technology in today’s solar photovoltaic (PV) market.

This innovation was published in natural energy on January 20, 2022. The research was conducted in collaboration with scientists from the University of Hong Kong and the Southern University of Science and Technology.

New trends in the solar world

Solar cell technology has seen tremendous growth in recent years as a sustainable energy source. The reliability, efficiency, durability and price of solar cells have a crucial impact on the commercial potential and the large-scale implementation of solar energy projects around the world.

Conventional solar cells used in solar power plants are based on a single junction architecture. The practical power conversion efficiency of single junction solar cells is limited to around 27% in industrial production. Pushing the frontiers of solar power generation will require new solutions for solar cells to perform better at converting energy.

In order to increase the power conversion efficiency of solar cells to go beyond 30%, stacks of two or more absorber layers (multi-junction cells) are required. Tandem solar cells, which are made from two different types of photovoltaic materials, are a hot area of ​​research.

In their latest project, Assistant Professor Hou and his team are innovating in the field of perovskite/organic tandem solar cells. Their discovery opens the door to lightweight and flexible thin-film tandem solar cells, which could have many applications such as blinds, vehicles, boats and other solar-powered mobile devices.

Breakthrough in power conversion efficiency

A tandem solar cell comprises two or more sub-cells electrically connected using interconnect layers (ICLs). The ICL plays a vital role in determining the performance and reproducibility of a device. An effective ICL must be chemically inert, electrically conductive and optically transparent.

Although perovskite/organic tandem solar cells are attractive for next-generation thin-film photovoltaics, their efficiency lags behind other types of tandem solar cells. To address this technological challenge, Asst Prof. Hou and his team developed a novel and efficient ICL that reduces voltage, optical and electrical losses in the tandem solar cell. This innovation dramatically improves the efficiency of perovskite/organic tandem solar cells, achieving a power conversion rate of 23.6%.

“Our study shows the great potential of perovskite-based tandem solar cells for future commercial applications of photovoltaic technology. Building on our new discovery, we hope to further improve the performance of our tandem solar cells and expand this technology “said Asst Prof. Whoa.