Nanostructure strategies for improved perovskite solar cells

Resumen del trabajo presentado en la Conferencia Española de Nanofotónica (CEN2021), celebrada de forma virtual del 20 al 22 de septiembre de 2021Organic-inorganic hybrid perovskite solar cells have attracted much attention due to their high power conversion efficiency (¿23%) and low-cost fabrication. Directions to further improve these solar cells include strategies to enhance their stability and their efficiency by modifying either the perovskite absorber layer or the electron/hole transport layer. For example, the transparent electron transport layer (ETL) can be an important tuning knob influencing the charge extraction, [1] light harvesting, [2] and stability [3] in these solar cells, or the use of up-conversion nanoparticles to get better performance in the near IR part of the visible spectrum. [4] Here we present two strategies based on nanostructuration, first a fundamental study of upconversion fluorescence enhancement effects near Au nanodisks by scanning near-field optical microscopy and second the effects of a nanocolumnar TiO2 layer on the performance and the stability of Cs0.05(FA0.83MA0.17)0.95Pb(I0.83Br0.17)3 perovskite solar cells. For the first case, the enhancement and localization of light near the metallic structures are directly visualized by using a single Er/Yb-codoped fluorescent nanocrystal glued at the end of a sharp scanning tip. [5] For the second we find that, compared to devices with planar TiO2 ETLs, the TiO2 nanocolumns can significantly enhance the power conversion efficiency of the perovskite solar cells by 17 % and prolong their shelf life. By analyzing the optical properties, solar cells characteristics, as well as transport/recombination properties by impedance spectroscopy, we observed light-trapping and reduced carrier recombination in solar cells associated with the use of TiO2 nanocolumn arrays. [6] References: [1] S.S. Mali, et al., Chemistry of Materials 27, 1541 (2015). [2] C. Liu, et al., Journal of Materials Chemistry A 5, 15970 (2017). [3] M. Salado, et al., Nano Energy 35, 215 (2017) [4] M. Bauch et al., Plasmonics 9, 781 (2014) [5] L. Aigouy, et al., Nanoscale 11, 10365 (2019) [6] Z. Hu, et al., ACS Appl. Mater. Interfaces 12, 5979 (2020

Microscopic Characterizations of Upconversion-Induced Near-Infrared Light Harvest in Hybrid Perovskite Solar Cells

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Mapping Plasmon-Enhanced Upconversion Fluorescence of Er/Yb-doped Nanocrystals Near Gold Nanodisks

Fluorescence enhancement effects have many potential applications in the domain of biochemical sensors and optoelectronic devices. Here, the emission properties of up-converting nanocrystals near nanostructures that support surface plasmon resonances have been investigated. Gold nanodisks of various diameters were illuminated in the near-infrared (λ = 975 nm) and a single fluorescent nanocrystal glued at the end of an atomic force microscope tip was scanned around them. By detecting its visible fluorescence around each structure, it is found that the highest fluorescence enhancement occurs in a zone that forms a two-lobe pattern near the nanodisks and which corresponds to the map of the near-field intensity calculated at the excitation wavelength. In agreement with numerical simulations, it is also observed that the maximum fluorescence enhancement takes place when the disk diameter is around 200 nm. Surprisingly, this disk size is small when compared to that yielding the highest far-field scattering resonance, which occurs for disks with a diameter of 300–350 nm at the same excitation wavelength. This shift between the near and far-field resonances should be taken into account in the design of structures in systems that use plasmon enhanced fluorescence effects.The authors thank the support from the DIM Nano-K program from “Région Ile de France”, from the Idex Paris Sciences & Lettres through the grant ANR-10-IDEX-0001-02 PSL, and from the CNRS and the CSIC through the Spanish-French program PICS (grant SolarNano #PICS07687 and #PIC2016FR2).Peer reviewe

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