A research team led by Prof. YE Jichun from the Ningbo Institute of Materials Technology and Engineering (NIMTE) of the Chinese Academy of Sciences, has developed a novel multifunctional cage-like diammonium chloride molecule. This molecule effectively minimizes interfacial energy losses, allowing the resulting perovskite/silicon tandem solar cells (TSCs) to achieve high efficiency and stability.

The findings were recently published in Nature Communications.

TSCs have emerged as a promising technology for the photovoltaic industry, thanks to their theoretically ultra-high efficiency and cost advantages. TSCs have attracted considerable research interest in recent years.

Despite a theoretical efficiency limit of 45.1%, significant room for improvement remains, especially for wide-bandgap perovskite top cells. A major barrier to reaching this theoretical limit is the substantial interfacial energy loss that occurs at the perovskite/electron-selective contact interface.

To address this bottleneck, the researchers synthesized the novel multifunctional cage-like diammonium chloride molecule and inserted it into the perovskite/C60 interface. This molecule acts to reduce film defects and modulate the interfacial dipole, thereby minimizing interfacial energy losses.

Using this approach, the team fabricated 1.68 eV perovskite solar cells that achieved power conversion efficiencies (PCEs): 22.6% on devices with a 0.1 cm² active area and 21.0% on those with a 1.21 cm² active area.

When integrated into a 1.0 cm² monolithic perovskite/silicon TSC, this optimized perovskite top cell enabled the tandem device to reach a PCE of 31.1%. Furthermore, the tandem device demonstrated long-term operational stability: it retained 85% of its initial efficiency after 1,020 hours of continuous maximum power point tracking under ambient conditions.

By resolving this critical interface issue, the study paves the way for the further development of efficient and stable perovskite-based tandem photovoltaic technologies.

The cage-like molecule enables high-performance perovskite/silicon tandem solar cells. (Image by NIMTE)