Charge Carrier Dynamics in Planar Heterojunction Organic Solar Cells

Yexiao Huang, Sein Chung, Safakath Karuthedath*, Catherine S.P. De Castro, Hua Tang, Minyoung Jeong, Shirong Lu, Kilwon Cho*, Frédéric Laquai, Zhipeng Kan*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

6 Scopus citations

Abstract

The ionization energy (IE) offset of a donor–acceptor pair provides the driving force for hole transfer and subsequent free charge carrier generation in low-bandgap nonfullerene organic solar cells (OSCs). However, the interfacial energetic landscape in bulk heterojunction OSCs is determined by the materials’ electronic structure and intermolecular interactions at the donor/acceptor interface, causing local energy-level shifts and disorder. Herein, the impact of the IE offset on the charge transfer efficiency and charge carrier dynamics is systematically evaluated by characterizing PM6/ITIC, PM6/IT-2Cl, and PM6/IT-4Cl planar heterojunction (PHJ) solar cells. Ultrafast spectroscopy and time-resolved charge carrier density measurements reveal that an IE offset of about ≈0.5 eV leads to efficient hole transfer and subsequent free charge generation. Furthermore, bimolecular charge recombination and consequently triplet generation are significantly reduced in systems with high IE offset. This work underlines the importance of sizeable donor–acceptor IE offsets in PHJ nonfullerene OSCs as critical for high-efficiency donor/acceptor material and device design.

Original languageEnglish (US)
Article number2300267
JournalSolar RRL
Volume7
Issue number12
DOIs
StatePublished - Jun 2023

Bibliographical note

Funding Information:
Y.H. and S.C. contributed equally to this work. The authors acknowledge financial support from Guangxi Natural Science Foundation (2022GXNSFDA035066), National Natural Science Foundation of China (62275057), Guangxi University (A3120051029). The research reported in this publication was supported by funding from the King Abdullah University of Science and Technology (KAUST) Office of Sponsored Research (OSR) under Award No. OSR‐CRG2018‐3746, under Award No. ORA‐CRG8‐2019‐4025, and National Research Foundation of Korea (NRF) grant (NRF‐2020R1A2C3004477) funded by the Ministry of Science and ICT (MSIT) of the Korean government. Portions of this research were carried out at the 3C and 9A beam lines of the Pohang Accelerator Laboratory, Republic of Korea.

Publisher Copyright:
© 2023 Wiley-VCH GmbH.

Keywords

  • bimolecular recombination
  • energetic disorder
  • hole transfer
  • planar heterojunction organic solar cells

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Atomic and Molecular Physics, and Optics
  • Energy Engineering and Power Technology
  • Electrical and Electronic Engineering

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