ALD ZnO Films for Stable Inverted Perovskite Solar Cells

Fernando Solorio Soto^a, Marko Topič^a, Marko Jošt^a

^aUniversity of Ljubljana, Faculty of Electrical Engineering, Trzaska cesta 25, SI-1000 Ljubljana, Slovenia, Ljubljana, Slovenia

Proceedings of MATSUS Spring 2026 Conference (MATSUSSpring26)

G3 Stability Challenges and Solutions in metal halide Perovskites materials

Barcelona, Spain, 2026 March 23rd - 27th

Organizers: Andres Fabian Gualdron Reyes, Sofia Masi and Teresa S. Ripolles

Oral, Fernando Solorio Soto, presentation 583
Publication date: 15th December 2025

Since perovskite solar cells (PSCs) were introduced to the photovoltaic (PV) field, research has predominantly focused on increasing their power conversion efficiency (PCE), achieving values comparable to state-of-the-art silicon technologies available on the market. Progress in extending long-term stability has followed, with devices often reaching t₈₀ values of several hundred hours; nevertheless, further improvements in long-term stability and understanding of degradation mechanisms are needed for commercialization.

PSCs degradation can be triggered by external factors such as UV light, temperature, and humidity, which cause ion migration given the ionic nature of perovskite. Here, adjacent layers play an important role in preventing metal ion diffusion and passivating the interface between the perovskite and charge transport layers. Electron transport layers (ETLs) based on fullerene (C₆₀) and its derivatives offer high electron mobility and reduced hysteresis; however, C₆₀-derivatives permeability allow ionic diffusion, leading to low stability.[1] The uniform characteristics of atomic layer deposition (ALD) enable the deposition of compact and pinhole-free materials. TiO₂, SnO₂, and ZnO are typical ETL candidates due to their band alignment, with SnO₂ remaining one of the preferred options. ZnO, which can serve as a blocking ion layer [2], has, perhaps unjustifiably, gradually fallen out of favor as it accelerates perovskite degradation when in direct contact due to its hygroscopic nature.[3], [4]

In this work, we demonstrate that incorporating ZnO films deposited by ALD into inverted PSCs improves long-term stability under continuous illumination. ZnO can act alone or in addition to SnO₂, on top of C₆₀. The latter case is especially important, as the use of ALD bilayers SnO₂|ZnO combines the higher power efficiency of SnO₂ with the improved stability provided by ZnO. The long-term stability of ZnO-containing cells improves by a factor of 2–3 compared to our reference cells, as confirmed by analyzing numerous (> 100) devices over several batches. In the best case, a t₈₀ of over 1100 hours has been reached. Several techniques, such as TEM, XPS, EQE, and PLQY, were used to elucidate the role of ALD ZnO films in improving stability.

References:

[1] Akbulatov, A. F., et al., Effect of Electron-Transport Material on Light-Induced Degradation of Inverted Planar Junction Perovskite Solar Cells. Adv Energy Mater 2017, 7, 19, 1700476.

[2] Rivkin, B.; Fassl, P.; Sun, Q.; Taylor, A. D.; Chen, Z.; Vaynzof, Y. Effect of Ion Migration-Induced Electrode Degradation on the Operational Stability of Perovskite Solar Cells. ACS Omega 2018, 3, 8, 10042–10047.

[3] Yang, J.; Siempelkamp, B. D.; Mosconi, E.; De Angelis, F.; Kelly, T. L. Origin of the Thermal Instability in CH3NH3PbI3 Thin Films Deposited on ZnO. Chemistry of Materials 2015, 27, 12, 4229–4236.

[4] Cheng, Y.; Yang, Q. D.; Xiao, J.; Xue, Q.; Li, H. W.; Guan, Z.; Yip, H. L.; Tsang, S. W. Decomposition of organometal halide perovskite films on zinc oxide nanoparticles. ACS Appl Mater Interfaces 2015, 7, 36, 19986–19993.

Acknowledgements:

We would like to thank ARIS for funding through research program P2-0415 and through the Gravity project GC-0003. F. Solorio also thanks ARIS for his PhD funding.

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