Understanding how bromine improves radiative recombination in formamidinium-based lead halide perovskites

Jesús Jiménez-López^a, E Laine Wong^a, Giulia Folpini^a, Ada Lilí Alvarado-Leaños^a^,^b, Antonella Treglia^a^,^b, Andrea Olivati^a^,^b, Daniele Cortecchia^a^,^c, Annamaria Petrozza^a

^aCenter for Nano Science and Technology @PoliMi, Istituto Italiano di Tecnologia, Milano, Italy

^bDipartimento di Fisica, Politecnico di Milano, Milan, Italy

^cDipartimento di Chimica Industriale ‘Toso Montanari’, Università di Bologna, Viale Risorgimento 4, 40136 Bologna, Italy

International Conference on Hybrid and Organic Photovoltaics
Proceedings of International Conference on Hybrid and Organic Photovoltaics (HOPV23)

London, United Kingdom, 2023 June 12th - 14th

Organizers: Tracey Clarke, James Durrant and Trystan Watson

Oral, Jesús Jiménez-López, presentation 197
DOI: https://doi.org/10.29363/nanoge.hopv.2023.197
Publication date: 30th March 2023

Formamidinium lead iodide (FAPbI₃) presents outstanding properties to be applied in different semiconductor applications. Its bandgap is ideal for achieving the highest solar-to-photocurrent power conversion efficiency in solar cells [1] and it is the material of choice for the development of near-infrared perovskite LEDs [2]. The design of effective passivation strategies requires a thorough understanding of defect-assisted recombination to fully exploit its potential.

Here, we explore the role of bromine (Br) introduction into FAPbI₃-based perovskites, an effective strategy previously used for solar cells [3], to promote their optoelectronic properties. Previous studies suggest that adding small amounts of Br into pure iodine perovskites results in a reduction of non-radiative recombination, either through deactivation of the detrimental short-lived hole-trapping [4], or the preferred orientation of the formamidinium cation towards the Br positions [5][6]. Thus, FAPbI₃-based perovskites would exhibit enhanced optoelectronic properties as a result of improved radiative recombination.

As a first step, we examined the effects of different amounts of Br on the morphology and optical properties of perovskite. Then, using a set of advanced spectroscopic techniques, including photo-emission electron microscopy, time-resolved photoluminescence, and ultrafast transient absorption spectroscopy, we visualized the reduction of the iodine-related defect states. Introducing Br in FAPbI₃ results in longer photoluminescence and carrier lifetimes, with improved photoluminescence quantum yields. Last, we confirmed the above findings by implementing Br containing FAPbI₃ in working LED devices, obtaining devices with reduced roll-off and increased radiances.

The use of small amounts of Br in formamidinium-based lead halide perovskites can thus be a promising alternative to address iodine-related defects, leading to improved radiative recombination properties.

References:

[1] Jeong, J.; Kim, M.; Seo, J.; Lu, H.; Ahlawat, P.; Mishra, A.; Yang, Y.; Hope, M. A.; Eickemeyer, F. T.; Kim, M.; Yoon, Y. J.; Choi, I. W.; Darwich, B. P.; Choi, S. J.; Jo, Y.; Lee, J. H.; Walker, B.; Zakeeruddin, S. M.; Emsley, L.; Rothlisberger, U.; Hagfeldt, A.; Kim, D. S.; Grätzel, M.; Kim, J. Y. Pseudo-Halide Anion Engineering for α-FAPbI3 Perovskite Solar Cells. Nature 2021, 592, 381–385.

[2] Cao, Y.; Wang, N.; Tian, H.; Guo, J.; Wei, Y.; Chen, H.; Miao, Y.; Zou, W.; Pan, K.; He, Y.; Cao, H.; Ke, Y.; Xu, M.; Wang, Y.; Yang, M.; Du, K.; Fu, Z.; Kong, D.; Dai, D.; Jin, Y.; Li, G.; Li, H.; Peng, Q.; Wang, J.; Huang, W. Perovskite Light-Emitting Diodes Based on Spontaneously Formed Submicrometre-Scale Structures. Nature 2018, 562, 249–253.

[3] Jeon, N. J.; Noh, J. H.; Yang, W. S.; Kim, Y. C.; Ryu, S.; Seo, J.; Seok, S. Il. Compositional Engineering of Perovskite Materials for High-Performance Solar Cells. Nature 2015, 517, 476–480.

[4] Meggiolaro, D.; Motti, S. G.; Mosconi, E.; Barker, A. J.; Ball, J.; Andrea Riccardo Perini, C.; Deschler, F.; Petrozza, A.; De Angelis, F. Iodine Chemistry Determines the Defect Tolerance of Lead-Halide Perovskites. Energy Environ. Sci. 2018, 11, 702–713.

[5] Johnston, A.; Walters, G.; Saidaminov, M. I.; Huang, Z.; Bertens, K.; Jalarvo, N.; Sargent, E. H. Bromine Incorporation and Suppressed Cation Rotation in Mixed-Halide Perovskites. ACS Nano 2020, 14, 15107–15118.

[6] Zhao, X.; Lu, H.; Fang, W.-H.; Long, R. Correlated Organic–Inorganic Motion Enhances Stability and Charge Carrier Lifetime in Mixed Halide Perovskites. Nanoscale 2022, 14, 4644–4653.

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