In the quest for superior solar energy solutions, inverted perovskite solar cells (IPSCs) hold great promise. However, stability issues—especially those arising at the interfaces between the perovskite and charge transport layers—significantly impede their commercialization progress. While the solution-processable fullerene derivative 58π-electron [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) is commonly used, it has a significant drawback: under continuous light exposure, it tends to dimerize, resulting in rapid performance degradation.
Now, a research team from China, led by Prof. Shangfeng Yang (University of Science and Technology of China), in collaboration with Prof. Fei Li (Anhui University), Prof. Zonglong Zhu and Prof. Xiao-Cheng Zeng (City University of Hong Kong), and Prof. Zhimin Fang (Yangzhou University), has developed a powerful countermeasure. They introduced two novel 56π-electron fullerene derivatives, named C 60 -TFB and C 60 -TFP, as high-performance electron transport layer (ETLs) that bring both efficiency and remarkable stability to IPSCs.
The researchers synthesized the two derivatives via a 1,4-unsymmetrical addition strategy, equipping the molecules with multiple bulky groups—including tert-butyl, indole, and azaindole units. These functional groups act like “molecular armor”, creating sufficient steric hindrance to effectively suppress dimerization.
Moreover, the heteroatom-rich structures help form strong interfacial binding with the perovskite layer and passivate surface defects. Together, these features promote the formation of a dense and uniform ETL, which acts as a robust barrier against the interdiffusion of iodide ions from the perovskite and silver atoms from the electrode—significantly enhancing interfacial integrity.
The results speak for themselves. The optimized C 60 -TFP-based IPSCs achieved a power conversion efficiency of 25.93%, a notable improvement over the 24.08% obtained from PCBM-based control devices.
More importantly, under continuous operational stress—over 1000 hours of illumination at 55 °C—the C 60 -TFP devices retained 81.9% of their initial efficiency, demonstrating outstanding operational stability. In contrast, the PCBM-based devices retained only 62.9%, underscoring the dramatic stability enhancement offered by the new derivative.
This work not only highlights the crucial role of tailored 56π-electron fullerene derivatives in stabilizing IPSCs but also opens a promising pathway toward designing charge transport materials for highly efficient and durable photovoltaic devices.
Professor Shangfeng Yang added that, coinciding with the 40th anniversary of the discovery of fullerene, he is confident that more novel fullerene-based electron transport materials will emerge for high-performance perovskite solar cells in the future.
National Science Review
Experimental study