Growth Controls the Charge Carriers of a 2D Ferroelectric Perovskite

Rhiannon Kennard^a, Clayton Dahlman^a, Juil Chung^a, Benjamin Cotts^b, Alexander Mikhailovsky^a, Lingling Mao^a, Ryan Decrescent^a, Kevin Stone^c, Naveen Venkatesan^a, Yahya Mohtashami^a, Sepanta Assadi^a, Alberto Salleo^b, Jon Schuller^a, Ram Seshadri^a, Michael Chabinyc^a

^aUniversity of California, Santa Barbara, Santa Barbara, United States

^bStanford University, Stanford, CA 94305, United States

^cStanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory Menlo Park, 94025, United States

Materials for Sustainable Development Conference (MATSUS)
Proceedings of nanoGe Fall Meeting 2021 (NFM21)

#PerEmer21. Perovskites III: Emerging Materials and Phenomena

Online, Spain, 2021 October 18th - 22nd

Organizers: Moritz Futscher, Jovana Milic and Aditya Mohite

Contributed talk, Rhiannon Kennard, presentation 161
DOI: https://doi.org/10.29363/nanoge.nfm.2021.161
Publication date: 23rd September 2021

The structural tunability of perovskites has paved the way for applications such as solar cells and resistive switching memory. Low-dimensional hybrid perovskites can be combined with 3D hybrid perovskites to make more stable solar cells. Interestingly, some low-dimensional hybrid perovskites also exhibit ferroelectricity, or the formation of electrically-polarized domains, making such materials attractive for resistive switching memory. For optoelectronic device applications, we must understand the behavior of the charge carriers, which in low-dimensional perovskites, is very diverse: free excitons, self-trapped excitons, phonon replicas, etc. In addition, because devices are primarily made from thin films, we must establish how the structural and optoelectronic properties of low dimensional perovskites might change with growth method.

Here, we investigate growth of the ferroelectric perovskite (EA)₄Pb₃Br₁₀. [1] We find that changing the growth method can be used funnel charge carriers into the free exciton or phonon-coupled states. Indeed, strains acquired from spin-coating turn off phonon-coupled emission. However, slower film growth methods preserve this phonon-coupled emission, and also increase domain size. Photothermal deflection spectroscopy shows that strain increases electronic disorder near the free exciton absorbance, which is undesired for solar cell applications. In addition, the challenge of making phase-pure films in low-dimensional Ruddlesden-Popper structure ((A’)2(A)n−1BnX3n+1) is overcome by using a single A/A’-site cation, ethylammonium (EA), whose optimal size also prohibits formation of off-target phases. This suggests that molecular design of the A/A’ sites might be used to favor phase purity in low-dimensional films. These results help extend the utility of 2D perovskites by providing design rules for how to grow films with the targeted phase and optoelectronic properties.

[1] Kennard, R.M., Dahlman, C.J., Chung, J., Cotts, B.L., Mikhailovsky, A.A, Mao, L., DeCrescent, R.A., Stone, K.H., Venkatesan, N.R., Mohtashami, Y., Assadi, S., Salleo, A., Schuller, J.A., Seshadri, R. and Chabinyc, M.L. Growth-Controlled Broad Emission in Phase-Pure Two-Dimensional Hybrid Perovskite Films. Accepted to Chemistry of Materials, 2021.

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