Chinese Researchers Uncover Aging Mechanism of Perovskite Solar Cells and Propose Longevity Solutions

Researchers from Nanjing University of Aeronautics and Astronautics have recently unveiled the aging mechanism of perovskite solar cells, providing a low-cost solution to extend their lifespan. This breakthrough is expected to accelerate the commercialization of the next generation of photovoltaic technology. The relevant paper was published online on May 30 in the prominent academic journal Science.

Professor Zhao Xiaoming explained that perovskite is a key candidate material for the next generation of photovoltaic technology. China is at the forefront of research in this field, with some small-sized perovskite solar cells achieving a power conversion efficiency exceeding 27%, comparable to that of commercial silicon-based solar cells. However, to transition perovskite from laboratory settings to production lines and gain market acceptance, challenges such as low conversion efficiency and short lifespan of large-sized perovskite solar cells must be addressed.

In the industry, the time it takes for the conversion efficiency to decline to 80% of its initial value is defined as the lifespan of a photovoltaic cell. The team led by Guo Wanlin and Zhao Xiaoming had previously developed a gas-phase fluorination technology that significantly improves the conversion efficiency and extends the lifespan of solar cells. However, this technology requires substantial modifications to existing production lines, increasing the financial burden on companies.

“To optimize the technology, we first needed to understand the essence of efficiency degradation,” Zhao Xiaoming noted. The team discovered that perovskite solar cells exhibit a phenomenon of “reversible degradation,” where the efficiency lost during the day partially recovers overnight after resting. “It’s akin to a person who feels tired after a long day but regains energy after a good night’s sleep,” explained Sun Xiangnan, the first author of the paper.

Further investigations revealed that this phenomenon is caused by the movement of iodide ions. During the day, under sunlight, these ions move around in the perovskite film, leading to the formation of tiny defects on the surface and a subsequent decrease in conversion efficiency. If the iodide ions remain within the perovskite layer, the degraded efficiency can automatically recover at night. However, if they migrate to the charge transport layer or electrodes, that efficiency is permanently lost.

Having identified the root cause, the team developed a “gas-phase assisted surface reconstruction” technology, which creates tiny isolation chambers on the surface of the perovskite film. This design confines the “troublesome” iodide ions, limiting their movement.

Experimental data showed that a large-sized perovskite solar cell, measuring 785 square centimeters and treated with the surface reconstruction technology, experienced only a 3% loss in conversion efficiency after 101 simulated day-night cycles at 50°C. “This is equivalent to being able to operate stably outdoors for 25 years,” Zhao Xiaoming stated.

To further evaluate the cell’s performance, the team subjected both perovskite and commercial silicon solar cells to high-temperature and high-humidity conditions for 45 days in summer and low-temperature conditions for 18 days in winter. The results indicated that the perovskite solar cells outperformed the silicon cells in both environments.

Importantly, the new technology is compatible with existing photovoltaic production lines, effectively controlling modification costs. Guo Wanlin emphasized that this research has achieved a closed-loop from theoretical foundation to practical application, clarifying the reasons behind the irreversible degradation of perovskite solar cells’ power conversion efficiency, and addressing a key bottleneck for the industrialization of large-sized perovskite technology. The team has applied for 10 patents and is currently refining the device fabrication process and material systems to expedite the launch of larger-sized perovskite solar cell pilot projects.