Proceedings of International Conference on Hybrid and Organic Photovoltaics (HOPV18)
DOI: https://doi.org/10.29363/nanoge.hopv.2018.158
Publication date: 21st February 2018
The radiative generation and recombination of charge carriers in semiconductors control both photovoltaic and LED operation. Understanding of these processes in metal-halide perovskites has advanced,1–4 but remains incomplete.
This talk, we will discuss the current question if an indirect nature of the band structure in metal-halide perovskites affects the radiative recombination of excited states. Using ultrafast transient absorption (TA) and photoluminescence (PL) experiments, we gain insights on the formation of emissive states at early times after photoexcitation. We find that the PL signal rises over two picoseconds while initially hot photo-generated carriers cool to the band edge. This shows that PL of hot carriers is slower than that of cold carriers, as expected from strongly-allowed radiative transitions. We conclude that electrons and holes show strong overlap in momentum space, despite the potential presence of a small band offset that we model to arise from a Rashba effect. We find that photon recycling processes further affect externally measured radiative recombination rates in hybrid perovskites. Taking into account photon recycling, we connect externally measured radiative efficiencies with the actual internal values, and derive internal PLQEs exceeding 80%. We discuss how elemental composition affects the recombination processes and luminescent yields.
(1) Johnston, M. B.; Herz, L. M. Hybrid Perovskites for Photovoltaics: Charge-Carrier Recombination, Diffusion, and Radiative Efficiencies. Acc. Chem. Res. 2016, 49, 146–154.
(2) Saba, M.; Cadelano, M.; Marongiu, D.; Chen, F.; Sarritzu, V.; Sestu, N.; Figus, C.; Aresti, M.; Piras, R.; Geddo Lehmann, A.; et al. Correlated Electron–hole Plasma in Organometal Perovskites. Nat. Commun. 2014, 5, 5049.
(3) Staub, F.; Hempel, H.; Hebig, J.-C.; Mock, J.; Paetzold, U. W.; Rau, U.; Unold, T.; Kirchartz, T. Beyond Bulk Lifetimes: Insights into Lead Halide Perovskite Films from Time-Resolved Photoluminescence. Phys. Rev. Appl. 2016, 6, 44017.
(4) Richter, J. M.; Abdi-Jalebi, M.; Sadhanala, A.; Tabachnyk, M.; Rivett, J. P. H.; Pazos-Outón, L. M.; Gödel, K. C.; Price, M.; Deschler, F.; Friend, R. H. Enhancing Photoluminescence Yields in Lead Halide Perovskites by Photon Recycling and Light out-Coupling. Nat. Commun. 2016, 7.
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International Conference on Hybrid and Organic Photovoltaics
International Conference on Hybrid and Organic Photovoltaics (HOPV) is celebrated yearly in May. The main topics are the development, function and modeling of materials and devices for hybrid and organic solar cells. The field is now dominated by perovskite solar cells but also other hybrid technologies, as organic solar cells, quantum dot solar cells, and dye-sensitized solar cells and their integration into devices for photoelectrochemical solar fuel production.
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