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Inhomogeneity in the structural and material quality of semiconductor nanowires (NWs) can lead to variation in the optical properties and functional performance. While often a challenge, this variation can provide insights into energy dynamics by characterising many NWs and identifying correlations between parameters [1]. In this work we study CsPbBr3 perovskites NWs grown epitaxially on c- and m-plane sapphire substrates. These NWs exhibit bright photoluminescence (PL) [2], a favourable photodetector response [3], strong wave-guiding [3] and can undergo lasing [4], making them promising for nanophotonics applications; however studying strain and surface recombination remains challenging.
The bandgap and carrier lifetimes of >10,000 NWs were extracted using automated PL spectroscopy and time-correlated single photon counting. A positive correlation was observed between the NW width and the bandgap due to strain at the substrate/NW interface. These results significantly extend a previous study of 10 NWs [5] and demonstrate that PL spectroscopy can be used to infer NW thicknesses up to 3um, with an uncertainty of ±0.25um, and hence is an accurate proxy for the geometry and surface-area. Bi-exponential carrier dynamics were observed, which were dominated by surface recombination with an 8ns lifetime for thin NWs, increasing to 10ns for wire thicknesses above 3um. Modelling of carrier diffusion and strain explains these dynamics and accounts for their variation across the NW population. Importantly, the large-scale data provides a route to study multiple aspects of nanowire growth and energy-dynamics from simple measurements.
[1] Parkinson, P. et al. (2020) Proc. SPIE 112910K.
[2] Oksenberg, E. et al (2018). Nano Letters, 18, 424.
[3] Shoaib, M. et al. (2017) J. Am. Chem. Soc. 139, 15592–15595.
[4] Schlaus, A. P. et al. (2019) Nat. Commun. 10, 265.
[5] Oksenberg, E. et al. (2020) Nat Commun. 11, 489.
| Speaker Country | United Kingdom |
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