Theoretical design of azaacene-based non-fullerene electron transport material used in inverted perovskite solar cells

ABSTRACT

Inverted perovskite solar cells (PSCs) have attracted much attention due to their low-temperature and solution-based process. Electron transport layers are important components in inverted PSCs. Non-fullerene n-type organic small molecules seem to be more attractive as electron transport layers, because their structures are easy to be synthesised and modified. In this paper, density functional theory and semi-classical Marcus electron transfer theory were used to explore the electron transport properties in three azaacene derivatives, including one experimentally reported molecule, 1,4,9,16-tetrakis((triisopropylsilyl)ethynyl)quinoxalino[2^‴,3^‴:4^″,5^″]cyclopenta[1^″,2^″,3^″:5^′,6^′]acenaphtho[1^′,2^′:5,6]pyrazino[2,3-b]phenazine (1), and two theoretically designed molecules (2 and 3). Compound 2 is formed by substituting i-Pr groups in compound 1 with H atoms, which is designed to evaluate the effect of i-Pr groups on the electron transport properties. Compound 3 is designed by adding one more benzopyrazine group to the conjugation structure of compound 1. It shows that i-Pr group can increase HOMO and LUMO energy levels and improve solubility in organic solvent and hydrophobicity. Enlarging conjugation can not only decrease LUMO energy level and electron reorganisation energy, but also can increase solubility and electron mobility. So our designed compound 3 is expected to be a potential electron transport material in inverted PSCs.

GRAPHICAL ABSTRACT

KEYWORDS:

• Inverted perovskite solar cell
• non-fullerene electron transport material
• reorganisation energy
• density functional theory

Acknowledgements

The authors thank the State Key Laboratory of Physical Chemistry of Solid Surfaces (Xiamen University) and National Supercomputing Centre in Shenzhen (Shenzhen Cloud Computing Centre) for providing computational resources and softwares.

Disclosure statement

No potential conflict of interest was reported by the authors.

ORCID

Wen-Peng Wuhttp://orcid.org/0000-0002-3851-9495

Xugeng Guo http://orcid.org/0000-0003-2152-2548

Jinglai Zhang http://orcid.org/0000-0002-2728-0511

Additional information

Funding

This work was supported by the National Natural Science Foundation of China (NSFC) [Grant Nos. 21676071 and 21703053]; Programme for Henan Innovative Research Team in University [Grant No. 15IRTSTHN005].