Defects, Interfaces, and Charge Extraction in Sn-Based Perovskite Nanocrystals and Solar Cells

QING SHEN^a

^aThe University of Elecro-Communications

Asia-Pacific International Conference on Perovskite, Organic Photovoltaics and Optoelectronics
Proceedings of Asia-Pacific International Conference on Perovskite, Organic Photovoltaics and Optoelectronics (IPEROP27)

Fukuoka, Japan, 2027 January 18th - 20th

Organizers: Zhanglin Guo and Tingli Ma

Invited Speaker Session, QING SHEN, presentation 056
Publication date: 22nd October 2026

Sn-based perovskites are attracting increasing attention as promising lead-free semiconductors for next-generation optoelectronic and photovoltaic applications. However, their performance and stability are still strongly limited by defect formation, oxidation of Sn(II) to Sn(IV), self-doping, and severe nonradiative carrier losses.

We have investigated defect control and charge-carrier dynamics in perovskite nanocrystals (PNCs), including Pb-, Sn–Pb-, and Sn-based systems [1–8]. Compositional engineering, metal doping, and control of Sn(IV)-related defects effectively suppress structural distortion and nonradiative recombination [5–8]. In particular, suppression of Sn(IV) formation enabled phase-stable Sn- and Sn–Pb-based PNCs with significantly improved optical properties and ultralong carrier lifetimes, providing new insight into the relationship between defect chemistry and carrier dynamics [7,8].

For Sn-based perovskite solar cells, whose power conversion efficiencies have exceeded 15% [9], we have further focused on the roles of interfacial defects in carrier recombination, transport, and extraction. Time-resolved photoluminescence measurements revealed pronounced carrier losses at the perovskite/electron-transport-layer interface, indicating that this interface is a major source of nonradiative recombination. Interfacial passivation effectively suppresses these losses, prolongs carrier lifetimes, and improves the open-circuit voltage.

More recently, using bias-modulated electrical transient measurements, we identified an extraction-limited charge-loss mechanism that is prominent in Sn-based solar cells but much less evident in high-efficiency Pb-based counterparts. Under high forward bias, interfacial defects and associated self-doping screen the internal electric field and hinder the extraction of low-mobility carriers. The resulting carrier accumulation enhances nonradiative recombination, thereby reducing both the open-circuit voltage and fill factor. These findings indicate that charge extraction, in addition to defect-mediated recombination, is a critical factor limiting the performance of Sn-based perovskite solar cells.

In this talk, I will discuss our recent progress in understanding and engineering defects, interfaces, and charge-extraction dynamics in Sn-based perovskite nanocrystals and solar cells, and highlight strategies toward more efficient and stable lead-free perovskite photovoltaics.

References:

[1] 1. Liu, F.; Zhang, Y.; Ding, C.; Kobayashi, S.; Izuishi, T.; Nakazawa, N.; Toyoda, T.; Ohta, T.; Hayase, S.; Minemoto, T.; Yoshino, K.; Dai, S.; Shen, Q. Highly Luminescent Phase-Stable CsPbI3 Perovskite Quantum Dots Achieving Near 100% Absolute Photoluminescence Quantum Yield. ACS Nano 2017, 11, 10373–10383.

[2] 2. Liu, F.; Ding, C.; Zhang, Y.; Ripolles, T. S.; Kamisaka, T.; Toyoda, T.; Hayase, S.; Minemoto, T.; Yoshino, K.; Dai, S.; Yanagida, M.; Noguchi, H.; Shen, Q. Colloidal Synthesis of Air-Stable Alloyed CsSn1–xPbxI3 Perovskite Nanocrystals for Use in Solar Cells. J. Am. Chem. Soc. 2017, 139, 16708–16719.

[3] 3. Liu, F.; Zhang, Y.; Ding, C.; Kawabata, K.; Yoshihara, Y.; Toyoda, T.; Hayase, S.; Minemoto, T.; Wang, R.; Shen, Q. Trioctylphosphine Oxide Acts as Alkahest for SnX2/PbX2: A General Synthetic Route to Perovskite ASnxPb1–xX3 (A = Cs, FA, MA; X = Cl, Br, I) Quantum Dots. Chem. Mater. 2020, 32, 1089–1100.

[4] Liu, F.; Jiang, J.; Zhang, Y.; Ding, C.; Toyoda, T.; Hayase, S.; Wang, R.; Tao, S.; Shen, Q. Near-Infrared Emission from Tin–Lead (Sn–Pb) Alloyed Perovskite Quantum Dots by Sodium Doping. Angew. Chem. Int. Ed. 2020, 59, 8421–8424.

[5] Jiang, J.; Liu, F.; Shen, Q.; Tao, S. X. The Role of Sodium in Stabilizing Tin–Lead (Sn–Pb) Alloyed Perovskite Quantum Dots. J. Mater. Chem. A 2021, 9, 12087–12098.

[6] 6. Liu, F.; Jiang, J.; Toyoda, T.; Kamarudin, M. A.; Hayase, S.; Wang, R.; Tao, S.; Shen, Q. Ultra-Halide-Rich Synthesis of Stable Pure Tin-Based Halide Perovskite Quantum Dots: Implications for Photovoltaics. ACS Appl. Nano Mater. 2021, 4, 3958–3968.

[7] 7. Li, Y.; Wang, D.; Yang, Y.; Ding, C.; Hu, Y.; Liu, F.; Wei, Y.; Liu, D.; Li, H.; Shi, G.; Chen, S.; Li, H.; Fuchimoto, A.; Tosa, K.; Hiroki, U.; Hayase, S.; Wei, H.; Shen, Q. Stable Inorganic Colloidal Tin and Tin–Lead Perovskite Nanocrystals with Ultralong Carrier Lifetime via Sn(IV) Control. J. Am. Chem. Soc. 2024, 146, 3094–3101.

[8] 8. Li, Y.; Jiang, J.; Wang, D.; Liu, D.; Yajima, S.; Li, H.; Fuchimoto, A.; Li, H.; Shi, G.; Hayase, S.; Tao, S.; Shi, J.; Meng, Q.; Ding, C.; Shen, Q. Electronic Coupling Between Perovskite Nanocrystal and Fullerene Modulates Hot Carrier Capture. Adv. Funct. Mater. 2025, 35, 2415735.

[9] 9. Wang, L.; Bi, H.; Liu, J.; Wei, Y.; Zhang, Z.; Chen, M.; Baranwal, A. K.; Kapil, G.; Kitamura, T.; Yang, S.; Miao, Q.; Shen, Q.; Ma, T.; Hayase, S. Exceeding 15% Performance with Energy Level Tuning in Tin-Based Perovskite Solar Cells. ACS Energy Lett. 2024, 9, 6238–6244.

[10] 10. Wang, J.; Gao, Z.; Yang, J.; Lv, M.; Chen, H.; Xue, D.-J.; Meng, X.; Yang, S. Controlling the Crystallization Kinetics of Lead-Free Tin Halide Perovskites for High Performance Green Photovoltaics. Adv. Energy Mater. 2021, 11, 2102131.

Acknowledgements:

This research was the Japan Science and Technology Agency (JST) Mirai program JPMJMI22E2) and MEXT KAKENHI Grant (24K01295, 26286013).

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