2D Lead-Free Inkjet-Printed Halide Perovskite Red-emitting LEDs on Rigid and Flexible Substrates
G. Vescio a b, D. Dirin c, J. Sanchez-Diaz d, S. Hernández a b, A. Cirera a b, I. Mora-Seró d, M. Kovalenko c, B. Garrido a b
a MIND, Department of Electronics and Biomedical Engineering, Universitat de Barcelona, Martí i Franquès 1, E-08028, Barcelona, Spain
b Institute of Nanoscience and Nanotechnology (IN2UB), Universitat de Barcelona, Av. Joan XXIII S/N, E-08028, Barcelona, Spain
c ETH Zürich, Kovalenko Lab - Functional Inorganic Materials, Anorganische Funktionsmaterialien, Vladimir-Prelog-Weg 1-5/10, 8093 Zürich, (Switzerland)
d Institute of Advanced Materials (INAM), Universitat Jaume I (UJI) Avenida de Vicent Sos Baynat, s/n, 12071 Castelló de la Plana, Spain
Proceedings of Sustainable Metal-halide perovskites for photovoltaics, optoelectronics and photonics (Sus-MHP)
València, Spain, 2022 December 12th - 13th
Organizers: Teresa S. Ripolles and Hui-Seon Kim
Oral, G. Vescio, presentation 034
Publication date: 15th November 2022

Halide Perovskites (HPs) have attracted attention over the past decade mostly due to their excellent optoelectronic properties for multiple applications in the field of photovoltaics (PVs) and perovskite light-emitting diodes (PeLEDs) due to their low no-radiative recombination. Despite their enormous potentiality the Pb content of HPs reporting the higher performance for different electronic devices is limiting the entrance in the market of this materials.

This fact has originated an intense work on Pb-free HP alternatives with very promising results in the last years in the field of PVs but significantly more limited in LED field. The studies of the applications of Pb-free perovskite to LEDs is still demonstrated in few works. Specifically, the more important issue is the poor film forming property that strongly depends on the deposition method. 3D HPs present low exciton binding energies and the use of low-dimensional structures is preferred for the fabrication of PeLEDs. Among low-dimensional structures, 2D halide HPs are receiving interest due to their natural quantum well structures, small Stokes shifts, narrow emission FWHM and lifetime on the order of nanoseconds. As in the case of Pb-free HP PVs most promising family for the development of PeLEDs are Sn-HPs. Nevertheless, despite the considerable progress in terms of performance achieved (EQE and luminance), Sn2+ in its oxidation state is prone to undergo oxidation in ambient conditions, forming its tetravalent state Sn4+. This fact causes a p-type self-doping process, leaving undesired Sn2+ vacancies that act as nonradiative recombination centres, thus quenching the perovskite emission.

Beyond materials demands, development of Sn-free PeLEDs will require industrial friendly fabrication methods, as spin-coating, the usual approach for deposition of 2D-layered PeLED devices, is a technique difficult to upscale, as does not offer selective deposition of LEDs in large areas and waste most of the precursors. In contrast inkjet printing is an emerging technology suitable to achieve smooth, uniform and pin-hole free thin films able to produce low-cost, large-area and even foldable-devices. Since its early beginnings, inkjet printing has attracted the attention of many researchers in the perovskite materials field, as it is believed to be the most feasible tool of patterning full color QD-LED display for mass production. This technique is especially attractive for the fabrication of LEDs arrays over large areas. Here, we present as the evolution from the first fabrication of Pb-Free HP PeLED i) on flexible substrate and ii) by inkjet printing deposition of the active layer. PeLEDs based on 2D PEA2SnI4 (PEA, phenyl ethyl ammonium) and TEA2SnI4 (TEA, 2-tiopheneethylammonium) have been fabricated by inkjet-printing technology, on both glass and polyimide flexible substrates, with red emission (630 nm for PEA2SnI4 and 640 nm for TEA2SnI4). Effect of using green solvent engineering in Sn-based perovskite LEDs will be also analyzed. Moreover, several additives can play an important diferent role in stabilization of both Sn-based red amitting LEDs.

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