Temperature-Dependent Studies and Spectroscopy of 2D-Layered Perovskite 2-thiophenemethylammonium lead iodide
Justas Deveikis a, Marcin Giza b, David Walker a, Nathaniel Gallop a, Pablo Docampo b, James Lloyd-Hughes a, Rebecca Milot a
a Department of Physics, University of Warwick, Coventry, United Kingdom
b School of Chemistry, University of Glasgow, Glasgow, United Kingdom
International Conference on Hybrid and Organic Photovoltaics
Proceedings of International Conference on Hybrid and Organic Photovoltaics (HOPV23)
London, United Kingdom, 2023 June 12th - 14th
Organizers: Tracey Clarke, James Durrant and Trystan Watson
Poster, Justas Deveikis, 254
Publication date: 30th March 2023

Temperature-dependent studies of perovskites provide fundamental information on optoelectronic properties and other temperature-induced effects in devices, such as thermal stress, film cracks, which impact performance and they are important to consider when designing the device. Temperature could induce changes in bandgap energy, photoluminescene (PL) lineshape [1]; structural lattice transitions could also occur, as shown in 3D perovskites by [2], [3], altering metal halide octahedra tilt angle and affecting electronic band structure.

In this work, we study changes in physical and optical properties in the 2D-layered perovskite, 2-thiophenemethylammonium lead iodide (ThMA2PbI4, predicted crystal structure shown in Fig. 1a, caused by temperature-induced structural phase transitions. We performed temperature-dependent X-ray diffraction, optical absorption, and PL measurements to investigate the lattice parameters and excitonic absorption/emission states in 100-300 K range.

A structural phase transition was observed at 220 K temperature, which was consistent across the three different measurements. From temperature-dependent XRD data in Fig. 1b, we found that c parameter of the lattice showed discontinuous contraction at 220 K by as the perovskite was heated, while thermal expansion coefficient in both phases was estimated to remain similar. Both ground state exciton absorption and PL peaks red-shifted across the phase transition temperature of 220 K as the sample was heated, as presented in Fig.1c and d. We noted an additional PL peak emerging at T<230 K red-shifted with respect of main excitonic peak and suggested it might be caused by trap-assisted exciton radiative recombination.

The temperature-dependent studies contribute to understanding the interaction between the organic spacer and inorganic lattice in the studied 2D-layered perovskite. We anticipate temperature variation may have caused reorientation of organic spacer altering the Pb-I-Pb angle modifying electronic band structure, in turn affecting the physical properties studied. Future work would focus on applying the methodology presented in this work to investigate 2D-layered perovskites with a variety of organic spacers.

The authors thank B. Breeze for the help with setting up temperature-dependent photoluminescence measurements.

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