Fluorination effects on bithiophene bridged hole transporting materials for perovskite solar cells

ABSTRACT

The use of hole transporting material (HTM) remains indispensable for efficient charge extraction in perovskite solar cells. In this work, a series of small-molecule HTMs are designed by introducing fluorine atoms into the central part of 2,2′-bithiophene core. The effect of fluorination on the photophysical, electrochemical, and hole transport properties is systematically explored using Quantum chemistry calculation. The Calculated results reveal that all the highest occupied molecular orbitals (HOMOs) and the lowest unoccupied molecular orbitals (LUMOs) of the studied molecules are well matched with the energy band structure of perovskite. Three fluorine substituted hole-transporting materials possess lower reorganisation energy than the reference molecule BT-MTP. The higher mobility and matched energy levels of predicted HTMs are beneficial for improving the performance of PSCs. All the designed HTMs display higher hole mobility than those of the BT-MTP. Especially, molecule DFBT-p-MTP exhibits better optical properties and stability, indicating that fluorination is an effective strategy to improve the performance of the device in real application. This work provides an avenue for designing low-cost small molecule HTMs for high-performance perovskite solar cells.

GRAPHICAL ABSTRACT

A series of fluorine substituted hole transporting materials are explored to reveal the relationship between the charge-transport properties and molecular engineering.

KEYWORDS:

• Hole-transporting materials
• first principle
• hole mobility
• hydrophobicity

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

We acknowledge generous financial support from the Youth Fund Project of the Engineering and Technical College of Chengdu University of Technology [C122022018], and Leshan's key science and technology project [21GZD027].