Complementary Photocurrent and Photothermal Characterisation of 2D Perovskite Light Emitting Diodes
Szymon J. Zelewski a, David O'Shea a b, Zher Ying Ooi a c, Yang Lu a, Samuel D. Stranks a c
a Cavendish Laboratory, Department of Physics, University of Cambridge, J.J. Thomson Avenue, Cambridge CB3 0HE, United Kingdom
b Clarendon Laboratory, Department of Physics, University of Oxford, Parks Road, Oxford OX1 3PU, United Kingdom
c Department of Chemical Engineering and Biotechnology, University of Cambridge, Philippa Fawcett Drive, Cambridge CB3 0AS, United Kingdom
Materials for Sustainable Development Conference (MATSUS)
Proceedings of MATSUS23 & Sustainable Technology Forum València (STECH23) (MATSUS23)
#2DPERO - 2D Perovskites: Synthesis, Properties, and Applications
València, Spain, 2023 March 6th - 10th
Organizers: Simon Kahmann and Loreta A. Muscarella
Poster, Szymon J. Zelewski, 355
Publication date: 22nd December 2022

Low-dimensional perovskite structures are at the forefront of light emitting applications, mainly owing to high carrier and exciton confinement. The ability to tune the emission wavelength through halide alloying and addition of organic cations promoting formation of 2D structure enables fabrication of light emitting diodes (LEDs) with external quantum efficiency comparable with solutions based on organic semiconductors, with the benefit of high colour purity. One of the challenges in the development of perovskite LEDs is their fundamental absorption-related optical characterisation, including assessing the influence of possible processes at the interfaces between electrodes and the active layer compared to the pristine material. Photocurrent spectroscopy remains the standard high-sensitivity technique for probing defect-related absorption and material disorder, applicable but limited to fully contacted devices, using LEDs in reverse as photodetectors. Here we demonstrate a complementary approach of incorporating modulated photocurrent and photothermal deflection spectroscopy (PDS) experiments for characterisation of 2D perovskite LEDs on different fabrication stages: bare perovskite thin films, the same deposited on top of transparent transport layers from the substrate-side (half-devices), and full LED structures. The results confirm that in optimised device preparation arrangements the sandwiched perovskite layer can fully preserve its optical quality, confirmed by quantifying absorption related to sub-gap trap states and sharpness of the absorption edge (the Urbach energy), revealing a crucial information for future development of LEDs.

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