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Overcoming the mobility penalty introduced by dipole disorder in small-molecule HTM films

Lookup NU author(s): Miriam Fsadni, Dr Thomas PopeORCiD, Dr Ivan Shmarov, Professor Thomas Penfold, Dr Pablo Docampo

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This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).


Abstract

The importance of the hole-transport material (HTM) in perovskite solar cells (PSCs) is now very well-established, with state-of-the-art materials such as Spiro-OMeTAD attracting significant attention in the last decade. The high cost of such materials still limits the commercialisation of these HTMs. To tackle this, the amide linker has recently been introduced into HTM systems via EDOT-Amide-TPA, utilising condensation chemistry as a cheap and effective route to HTMs. EDOT-Amide-TPA is capable of a variety of intermolecular interactions such as dipole-dipole interactions and hydrogen bonding, both of which are beneficial for enhancing the film morphology and improving charge transport. However, the interplay between these different interactions is not trivial, and understanding how they affect each other is paramount to inform new HTM designs whilst minimising material waste. To date, studies investigating the combined effects of different intermolecular interactions within the HTL on the charge transport properties of these materials are lacking. Furthermore, dipole disorder within the film introduces a mobility ‘penalty’: mobility decreases with stronger overall dipole due to energetic disorder within the film, which hinders charge hopping. In this work, we investigate three amide-based HTM analogs with differing intermolecular interaction capabilities, and show that this penalty can be compensated by a preferentially increased dipole ordering, likely achieved through intermolecular hydrogen bonding. This effectively cancels out the dipole disorder while retaining the beneficial effects on the molecular packing. Our aim is that this work provides a good foundation for navigating the complex interplay between hydrogen bonding, dipole moments, conductivity, and film formation in small-molecule HTMs


Publication metadata

Author(s): Vella B, Fsadni MH, Pope T, Giza M, Angus F, Shmarov I, Lalaguna PL, Cariello M, Wilson C, Kadodwala M, Penfold T, Docampo P, Cooke G

Publication type: Article

Publication status: Published

Journal: Journal of Materials Chemistry A

Year: 2024

Pages: epub ahead of print

Online publication date: 25/07/2024

Acceptance date: 25/07/2024

Date deposited: 31/07/2024

ISSN (print): 2050-7488

ISSN (electronic): 2050-7496

Publisher: Royal Society of Chemistry

URL: https://doi.org/10.1039/D4TA00956H

DOI: 10.1039/D4TA00956H

Data Access Statement: Crystal structures for the amide compounds in this study have been deposited into the CCDC. CCDC Deposition numbers are: EDOT-Amide-TPA (Compound 1): Deposition number 2301541, Unit cell parameters: a 55.7783(6) b 55.7783(6) c 10.4905(2) I41/a DEDOT-Amide-TPA (Compound 2): Deposition number 2301539, Unit cell parameters: a 16.6681(5) b 18.0603(6) c 16.6318(5) P21/c TPABT (Compound 3): Deposition number 2301540, Unit cell parameters: a 12.1294(3) b 14.8596(3) c 27.9555(8) P21/c. Other data supporting this article have been included as part of the ESI.


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Funding

Funder referenceFunder name
EP/SO23836/1
EP/E036244/1
EP/T010568/1EPSRC
EP/T022442/1
EP/V027425/1
EPSRC
University of Glasgow

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