Narrow bandgap Pb-Sn Perovskite Solar cells with high Voc via Surface Passivation and Additive Engineering

Marina Ustinova^a^,^b, Erica Magliano^b^,^a, Renhao Zheng^a, Francesco Toschi^b, Federico Trezzini^a, Aldo Di Carlo^a^,^b

^aCHOSE – Dept. Electronic Engineering University of Rome Tor Vergata, Casale 11, Rome, 00133 Italy

^bCNR-ISM Istituto di Struttura Della Materia, Consiglio Nazionale Delle Ricerche, Roma Tor Vergata, Rome, 00133 Italy

NIPHO25
Proceedings of International Conference on Perovskite Thin Film Photovoltaics and Perovskite Photonics and Optoelectronics (NIPHO25)

Cagliari, Italy, 2025 June 9th - 10th

Organizers: Giulia Grancini, Daniela Marongiu and Aldo Di Carlo

Oral, Marina Ustinova, presentation 031
Publication date: 24th April 2025

The power conversion efficiency (PCE) of single junction Pb-Sn perovskite solar cells has overcome the threshold of 24% [1]. Their use is especially promising for the fabrication of tandem solar cells to surpass the efficiency limits. However, rapid oxidation of Sn²⁺ cations during fabrication process and operation of solar cells affects the V_OC. In addition, the solution-based process of fabrication is complicated by non-uniform crystallization of the perovskite phase and very sensitive to changes in conditions, in particular temperature. In this work, to improve the morphology of Pb-Sn perovskite films, different methods of quenching (vacuum, N₂ gas flow, and antisolvent) during the spin-coating process were applied. Furthermore, we present a comparative study of the influence of various additives (metal halides, thiocyanate salts, phenylethylammonium (PEA) halides and their fluorine-containing derivatives) on the performance of Pb-Sn perovskite solar cells with 1.26 eV bandgap. The surface treatment of perovskite films with ethylenediamine (EDA), EDAI₂, butane-1,4-diamine iodide (BDAI₂), PEAI, and 4F-PEAI solutions was also applied in comparison. The best combination of additives and surface passivators significantly enhanced V_OC and FF of the APb_0.5Sn_0.5I₃ solar cells (A=Cs, MA, and FA). The stabilized PCE of 18.6 % was achieved in the encapsulated p-i-n single junction solar cells with the structure of ITO/PEDOT:PSS/perovskite/PCBM/BCP/Cu (V_OC =0.87 V, J_SC =27.5 mA/cm², and FF=77.7%). However, the previously reported combination of additives (SnF₂, guanidine thiocyanate and PEAI) taken as a reference [2] provided only 16.45% (V_OC =0.80 V, J_SC = 27.4 mA/cm², and FF=75.1%). The obtained solar cells were applied as bottom subcells in the 4-terminal all-perovskite tandem cells, providing the PCE of >23 % in preliminary measurements.

References:

[1] Zhang, Y.; Li, C.; Zhao, H.; Yu, Z.; Tang, X.; Zhang, J.; Chen, Z.; Zeng, J.; Zhang, P.; Han, L; Chen, H. Synchronized crystallization in tin-lead perovskite solar cells. Nat. Commun. 2024, 15, 1, 6887.

[2] Tong, J.; Jiang, Q.; Ferguson, A. J.; Palmstrom, A. F.; Wang, X.; Hao, J.; Dunfield, S.P.; Louks, A.E.; Harvey, S.P.; Li, C.; Lu, H.; France, R.M.; Johnson, S.A.; Zhang, F.; Yang, M.; Geisz, J.F.; McGehee, MD.; Beard, M.C.; Yan, Y.; Kuciauskas D.; Berry, J.J.; Zhu, K. Carrier control in Sn–Pb perovskites via 2D cation engineering for all-perovskite tandem solar cells with improved efficiency and stability. Nat. Energy. 2022, 7, 7, 642-651.

Acknowledgements:

We acknowledge the GOPV project RdS2019-21 CSEAA_00011 - TIPO A - Ministry of Environment and Energy Security (MASE) – CUP E83C23000840001

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