Research Paper: Defect mitigation via fullerene-based functional additives for enhanced efficiency and stability in tin perovskite solar cells

Summary

This study addresses the instability and low efficiency of lead-free tin-based perovskite solar cells (Sn-PSCs) by introducing fullerene-based multifunctional additives to mitigate defects. The main goal was to stabilize tin in its reduced Sn2+ state, preventing oxidation to Sn4+, which causes structural defects and compromises device performance. Key findings reveal that fullerene derivatives, particularly F-COOH, significantly suppress Sn4+ formation and non-radiative recombination. F-COOH-treated devices achieved a notable increase in power conversion efficiency (PCE) from 8.20% to 11.22%, with improved VOC, JSC, and fill factor. This enhancement is attributed to F-COOH's ability to moderate crystallization, leading to a more uniform film morphology with fewer bulk and interfacial defects, and strong interaction with Sn2+. F-COOH also significantly enhanced operational stability, retaining over 51% of initial efficiency after 500 hours compared to 35% for control devices. Theoretical calculations corroborate F-COOH's superior defect passivation and strong binding to the perovskite surface.

Why it Matters

Tin-based perovskite solar cells are a promising, environmentally benign alternative to lead-based counterparts but suffer from rapid Sn2+ oxidation and instability. This research provides a crucial strategy using functional additives to overcome these limitations, offering a clear pathway for developing high-efficiency, stable, and lead-free solar cell technologies. The findings highlight the critical importance of functional group selection in molecular design, which is essential for advancing sustainable photovoltaic solutions and accelerating their commercial viability.

Fluxim Tools Used

The PAIOS (Fluxim AG) all-in-one characterisation system was employed for transient photovoltage (TPV), transient photocurrent (TPC), capacitance-frequency (C-f), and capacitance-voltage (C-V) measurements. These measurements were crucial for gaining insights into the device's charge carrier dynamics, interface states, trap states, defect density profiles, and efficient charge extraction. The data obtained from PAIOS directly supported the conclusions regarding reduced trap-assisted recombination, longer carrier lifetimes, and improved charge extraction in the F-COOH modified devices.

Publication Details

Shukla, A., Khadka, D.B., Li, C., Rikukawa, M., Takeoka, Y., Sahara, R., Yanagida, M. and Shirai, Y. (2025), Defect mitigation via fullerene-based functional additives for enhanced efficiency and stability in tin perovskite solar cells. J. Mater. Chem. A, 13: 23487. https://doi.org/10.1039/d4ta08566c