“Collectively, these advancements offer ground-breaking insights into mitigating energy loss in perovskite solar cells,” said assistant professor Hou Yi (right). Image: NUS

Scientists at the National University of Singapore (NUS) have created a groundbreaking triple-junction perovskite/silicon tandem solar cell, achieving a record power conversion efficiency of 27.1% over a 1cm2 area.

In recent years, tandem solar cells have garnered significant interest among researchers due to their ability to significantly broaden the spectrum of sunlight that can be converted into electricity by utilizing multiple junctions within the same cell. According to the US Department of Energy, while the maximum conversion efficiency of a single-junction cell hovers around 33.5%, multiple-junction cells boast a maximum efficiency of “over 45%”.

In a significant breakthrough last year, LONGi, a Chinese manufacturer, achieved a record power conversion efficiency of 33.9% with their crystalline silicon-perovskite tandem cell. Although the NUS cell does not surpass this value, it represents an important advancement that builds upon the progress made by LONGi.

The NUS cell is comprised of three individual cells, with two of them being a perovskite solar cell and a silicon solar cell. These cells were stacked together by the researchers to form a dual-junction cell. To enhance the stability and establish crucial interactions within the perovskite, the team introduced a third cell that incorporates cyanate, a negatively-charged ion.

The researchers dedicated a significant portion of their study to examining the effects of incorporating cyanate. They discovered that perovskite solar cells utilizing this ion were capable of generating 1.422 volts, in contrast to the 1.357 volts produced by conventional perovskite cells. The scientists noted that this improvement resulted in a substantial reduction in energy loss.

“Ground-breaking insights”

Assistant Professor Hou Yi, who led the team from the NUS College of Design and Engineering and the Solar Energy Research Institute of Singapore in developing the triple-junction cell, expressed great enthusiasm for their achievement. He stated, “Remarkably, after 15 years of continuous research in the field of perovskite-based solar cells, this work provides the first experimental evidence of incorporating cyanate into perovskites to enhance structural stability and improve power conversion efficiency.”

Hou further emphasized the significance of these advancements, stating, “Together, these breakthroughs provide groundbreaking insights into reducing energy loss in perovskite solar cells and chart a new path for the continued advancement of perovskite-based triple junction solar technology.”

The recent findings bring positive prospects for triple-junction solar cells as a whole. In a notable achievement last year, scientists at the Fraunhofer Institute for Solar Energy Systems (Fraunhofer ISE) created a triple-junction cell incorporating two perovskite layers and one silicon layer, achieving an impressive conversion efficiency of over 30.0%. This outcome suggests that the inclusion of cyanate in the NUS cell could have had a substantial influence on its performance.

In a recent breakthrough, scientists from Fraunhofer ISE and Oxford PV collaborated to create a full-sized tandem PV module with an unprecedented power conversion efficiency of 25%. This achievement sets a new record for a module of this size and underscores the ongoing commitment of the solar industry to invest in research and explore new opportunities.