China’s next-gen solar cell hits 27.2% efficiency, endures 1,000 hours at 185°F

Researchers at the Institute of Semiconductors, part of the Chinese Academy of Sciences, have developed a perovskite solar cell prototype with a certified photoconversion efficiency of 27.2%. 

The findings, which detail a method for addressing a key stability issue, were published in the journal Science. The certified steady-state efficiency was measured on a device area of 0.108 square centimeters.

The devices also demonstrated improved operational stability. The new cells were subjected to long-duration testing, retaining 86.3% of their initial efficiency after 1,529 hours of continuous operation under 1 Sun illumination at their maximum power point (MPPT).

In an accelerated aging test, an unpassivated device was exposed to continuous 1 Sun illumination and a constant temperature of 185°F. 

Under these conditions, the cell maintained 82.8% of its original efficiency after 1,000 hours, indicating improved durability against heat and light.

Addressing film inhomogeneity

The team’s research focused on a known problem in perovskite film fabrication. An additive commonly used to help grow formamidinium lead iodide films, methylammonium chloride, was found to cause an uneven distribution of chloride ions.

The researchers observed that during the crystallization phase, chloride ions tend to migrate and accumulate near the film’s top surface.

This phenomenon, described as “through-film inhomogeneity,” leads to the formation of surface defects and interfacial barriers. These flaws impede the flow of electrons, reducing the cell’s power output and creating pathways for the material to degrade.

“The uneven distribution of ions from the additives used to improve perovskite films is a major problem for solar cells made of these materials,” highlighted the study. 

Stabilizing the film with a new additive

To counteract this ion migration, the scientific team introduced a different compound, alkali metal oxalate (specifically potassium binoxalate), during the film’s thermal processing. They found that this compound thermally dissociates (breaks down with heat) during the manufacturing step.

This dissociation releases positively charged potassium ions. These potassium ions have a strong chemical affinity for the negatively charged chloride ions and bind to them, forming potassium chloride. 

This mechanism prevents the uncontrolled migration of chloride ions to the surface and promotes a uniform distribution of chlorine throughout the perovskite layer. This method allowed the team to fabricate films that are more efficient and more durable.

Other related developments

Earlier, in another development, an international team of researchers raised the efficiency of perovskite solar cells to nearly 27 percent after introducing a new interfacial coating between the top contact and the perovskite layer. 

Their approach involved creating a thin, fluorinated molecular layer that acts as a chemical shield between the perovskite and its top contact layer, known as the buckyball (C60) layer.

The approach could bridge that gap, offering a scalable solution that combines high performance with long-term resilience. It could also speed up the creation of new solar technologies, from rooftop installations to flexible devices and tandem solar modules.