Solar cells retain 96% efficiency after 1,200 hours with new material

Researchers from the National University of Singapore (NUS) have engineered a method to enhance the durability of perovskite-silicon tandem solar cells. 

This enables the devices to retain over 96% of their initial performance after 1,200 hours of continuous operation at 149°F.

The study details a new molecular design that improves the interface between cell layers. 

“With the new cross-linked layer in place, the NUS researchers’ perovskite-silicon tandem cells achieved efficiencies above 34 per cent, including a certified 33.6 per cent from an independent testing centre,” said the researchers in a press release.

Identifying the stability bottleneck

Perovskite-silicon tandem solar cells combine two distinct materials to capture a broader spectrum of sunlight than traditional silicon panels. While these hybrid devices have theoretically reached efficiencies of nearly 35 per cent, their deployment has been limited by instability issues. 

Commercial silicon panels typically operate reliably for 20 to 25 years, a standard that next-generation tandem designs have struggled to meet due to rapid degradation under heat.

The research team, led by Assistant Professor Park Somin from the Department of Chemistry in the NUS Faculty of Science, initiated the study by recreating high-efficiency tandem cells described in existing literature. 

By subjecting these cells to sustained light and heat, they determined that the primary failure point was not the perovskite material itself, as previously hypothesised, but the ultra-thin contact layer connecting the perovskite to the silicon.

Modifying the molecular interface

This contact layer, known as a self-assembled monolayer (SAM), serves as a “hole-transport” layer that facilitates the flow of electrical charge. The researchers observed that conventional SAMs lose their orderly structure when exposed to elevated temperatures.

Assistant Professor Wei Mingyang from the Department of Materials Science and Engineering at the NUS College of Design and Engineering explained the mechanical failure.

“Conventional SAMs act like a carpet of molecules that helps charges move across,” added Assistant Professor Wei. 

“When they get too warm, the fibres start curling up, leaving gaps that block the flow of electricity.”

To address this, the team developed a modified SAM capable of forming a cross-linked network. 

“The molecules form tiny chemical links with one another as they assemble, creating a tightly bound layer that resists heat and maintains its structure during operation,” explained the press release.

“This cross-linked molecular contact improved the interface between the layers and helped the entire solar cell retain high efficiency over time.”

Path toward commercial application

The development aims to align the operational lifespan of tandem cells with current industrial standards. 

Assistant Professor Park noted that for these cells to be viable alternatives to traditional panels, they must maintain stability in field conditions without requiring complex manufacturing processes.

“We focused on strengthening the weakest link — the ultra-thin molecular layer between the two materials,” concluded Assistant Professor Park. 

“Identifying the root cause of the performance degradation – the SAM, and then reinforcing it, is the breakthrough needed to enhance the stability of these solar cells.”