Beyond 2100 Hours: ETU-Stabilized Perovskite Solar Cells Demonstrate Exceptional Lifetime on Fluxim's Litos Platform

In this work, we report a significant advance in the operational stability of formamidinium-rich (FA-rich) perovskite solar cells by suppressing stacking faults through a simple additive strategy. Using nanostructure characterization techniques, we identified that degradation frequently initiates at stacking faults pathways within (011)-faceted perovskite domains in different leading FA-rich perovskite compositions. To mitigate this, we introduced Ethylene Thiourea (ETU) into the perovskite precursor solution. 

ETU induced a preferential growth of (001)-oriented domains both in-plane and out-of-plane, suppressing the formation of (011) facets.  

Fig 1. X-ray diffractogram confirming the suppression of (011) perovskite planes in the ETU-treated target film. 

This was further evidenced by 4D-STEM orientation mapping. 

Figure 2. Orientation map highlighting the alignment of perovskite domains along the [001]C zone axis in the ETU-treated film.

Density functional theory calculations supported these findings, showing that ETU lowers the perovskite formation energy, enabling room-temperature crystallization without antisolvent quenching. This facilitated the fabrication of large-area, high-quality blade-coated perovskite films and devices. 

Key stability results acquired using the Fluxim Litos platform: 

• >93% PCE retention after 2100 hours under continuous MPP tracking with 1 SE white LED illumination 
  (ISOS-L1 protocol, ambient, encapsulated, 0.2 cm² devices) 

• T80 >600 hours at 65 °C under 1-sun illumination 
  (1 cm² encapsulated devices- characterized independently; Litos was used in the broader stability campaign) 

• T80 ~7200 hours at 65 °C for masked 0.2 cm² devices 
  (among the best results reported to date) 

Fig 3. Normalized MPP tracking: 0.2 cm² encapsulated devices retain >93% initial PCE after 2100 h, measured with Litos. 

These results were obtained using the Fluxim Litos platform, which provided controlled temperature and illumination, continuous MPP tracking, and real-time data logging—essential for rigorous lifetime validation. 

Figure 4. Litos by Fluxim – an advanced stability testing system for solar cells and LEDs. 

Accelerated testing at elevated temperatures also demonstrated remarkable performance:

Figure 5. Normalized MPP tracking for 1 cm² devices at 65 °C. T80 >600 hours. 

Figure 6. Stability of masked 0.2 cm² devices at 65 °C, showing ~95% PCE retention at 1800 h. 

“The Fluxim Litos platform played a crucial role in acquiring high-quality stability data. The ability to test under controlled illumination and temperature while continuously tracking MPP provided reliable insights into long-term device performance. The option to have independently operatable measurement chambers allowed us to obtain stability data for multiple test conditions in parallel, which is a big advantage of Litos.” 

Mostafa Othman 

PhD Student, Laboratory of Photovoltaics and Electronic thin Films, EPFL. 

This study highlights the value of additive-driven crystal facet engineering to improve perovskite stability, while showcasing how advanced tools like Litos enable robust, real-world validation of breakthrough solar cell technologies. 

Reference 
 

M. Othman, L. Agosta, Q. Jeangros, A. Jaffrès, S. Jenatsch, V. Carnevali, N. Lempesis, V. Slama, J. A. Steele, R. Zhang, E. Solano, G. Portale, V. Boureau, A. Paracchino, A. Bornet, H. Lai, F. Fu, A. K. Sachan, W. Tress, K. Artuk, M. D. Mensi, M. R. Golobostanfard, A. G. Kuba, S. Zeiske, A. Armin, N. Blondiaux, L. Champault, U. Röthlisberger, B. Ruhstaller, C. Ballif, A. Hessler-Wyser, C. M. Wolff, Suppression of Stacking Faults for Stable Formamidinium-Rich Perovskite Absorbers. Adv. Mater. 2025, 2502142. https://doi.org/10.1002/adma.202502142