China’s new inverted perovskite solar modules retain 94% efficiency after 1000 hours

A global research team led by the University of Electronic Science and Technology of China (UESTC) has made a breakthrough in perovskite solar technology.

By adding pyrrodiazole (PZ) to formamidinium iodide (FAI)-based perovskite films, researchers improved the stability of perovskite layers and enabled large-scale production using slot-die coating in air.

Perovskite solar cells come in two primary structures: conventional “n-i-p” and inverted “p-i-n.” In the inverted structure, the hole-selective contact (p) is at the bottom, while the electron transport layer (n) is on top. This design allows light to enter through the hole transport layer (HTL), unlike n-i-p cells, where illumination occurs through the electron transport layer (ETL).

“We achieved the scalable preparation of homogeneous structure perovskite films via regulating the crystallization process of perovskite through immobilizing strategy,” said Shibin Li, the corresponding author of the study, as reported by PV Magazine.

Improved efficiency and durability

The PZ additive was critical in stabilizing lead iodide (PbI2) and FAI during crystallization. Researchers found that PZ formed strong Lewis acid-base pairs with PbI2 and hydrogen bonds with FAI. This interaction reduced colloidal aggregation, improving film uniformity and preventing defects.

The team developed a multi-layered solar cell structure consisting of transparent fluorine-doped tin oxide (FTO) glass substrate, a sputtered nickel(II) oxide (NiOx) film, a methyl-substituted carbazole (Me-4PACz) layer, the perovskite film, a buckminsterfullerene (C60) electron transport layer, a bathocuproine (BCP) buffer layer, and a copper (Cu) contact.

The Me-4PACz layer was applied using blade coating, followed by perovskite deposition via slot-die coating in open-air conditions. The real-time analysis showed that this method slowed crystal growth while maintaining even crystallization throughout the film, producing large, uniform perovskite grains.

The mini solar modules developed using this method reached a peak efficiency of 21.5% and a certified efficiency of 20.3%—one of the highest reported efficiencies for inverted perovskite solar modules with an aperture area exceeding 50 cm². The modules also demonstrated long-term stability, retaining 94% of their initial efficiency after 1,000 hours of continuous light exposure in the air under 65% relative humidity.

Future applications in large-scale solar energy

The experiment used 3.94 inches × 3.94 inches (10 cm × 10 cm) perovskite solar modules containing 11 connected sub-cells. China’s National Institute of Measurement and Testing Technology validated the modules’ performance.

Further tests on modules with a 56.5 cm² aperture area showed that PZ-enhanced modules improved efficiency from 18.2% to 21.5%. However, variations of the PZ additive, labeled PZ-I and PZ-II, had minimal or negative effects, achieving 17.9% and 17.0% efficiency, respectively.

“We will focus on optimizing the efficiency and stability of large-area perovskite-silicon tandem solar cells,” said Li, emphasizing the team’s future research direction.

This innovation could lead to more efficient and scalable solar panel production, bringing perovskite technology closer to widespread commercial adoption.

The research, published in Nature Communications, involved scientists from UESTC, Guangzhou University, China Jiliang University, and the Institut de Recherche de Chimie Paris (IRCP) in France.