Scientists in Singapore have developed a cell that could be used to power vehicles and boats, among other applications. The tandem device purportedly retains 90% initial efficiency after 500 hours of maximum power point tracking under continuous one sun illumination.

National University of Singapore (NUS) researchers have fabricated a perovskite/organic tandem solar cell with an optimized interconnecting layer (ICL) structure based on a 4-nanometer sputtered indium zinc oxide layer.

They described the cell in “Monolithic perovskite/organic tandem solar cells with 23.6% efficiency enabled by reduced voltage losses and optimized interconnecting layer,” which was recently published in Nature Energy. It has lower voltage, optical and electrical losses compared to other tandem cells of the same kind, which are usually limited by open-circuit voltage losses in the wide-bandgap perovskite subcells.

The research team said that ICLs are crucial for the performance and reproducibility of a tandem cell. An effective ICL should be chemically inert, electrically conductive and optically transparent, they explained.

The perovskite subcell’s nickel oxide hole-transporting layers were passivated with benzylphosphonic acid leads. The scientists did this to suppress interfacial recombination, which in perovskite cells has a deep influence on electrical performance, including open-circuit voltage, short-circuit current, fill factor, and ultimately, power conversion efficiency.

As a result, the subcell achieved a voltage up to 1.26V in a 1.79-eV-bandgap and the overall tandem cell efficiency reached 23.6%, a value that compares to around 20% in solar cells with the same tandem architecture.

“In addition, the tandem device retained 90% initial efficiency after 500 h maximum power point tracking under continuous one sun illumination,” the scientists said. “This technological breakthrough paves the way for flexible, lightweight, low cost and ultra-thin photovoltaic cells which are ideal for powering vehicles, boats, blinds and other applications.”