Correlating the Hybridization of Local-Exciton and Charge-Transfer States with Charge Generation in Organic Solar Cells

Deping Qian, Saied Md Pratik, Qi Liu, Yifan Dong, Rui Zhang, Jianwei Yu, Nicola Gasparini, Jiaying Wu, Tiankai Zhang, Veaceslav Coropceanu, Xia Guo, Maojie Zhang, Jean Luc Bredas, Feng Gao, James R. Durrant

Research output: Contribution to journalArticlepeer-review

4 Scopus citations

Abstract

In organic solar cells with very small energetic-offset (ΔELE − CT), the charge-transfer (CT) and local-exciton (LE) states strongly interact via electronic hybridization and thermal population effects, suppressing the non-radiative recombination. Here, we investigated the impact of these effects on charge generation and recombination. In the blends of PTO2:C8IC and PTO2:Y6 with very small, ultra-fast CT state formation was observed, and assigned to direct photoexcitation resulting from strong hybridization of the LE and CT states (i.e., LE-CT intermixed states). These states in turn accelerate the recombination of both CT and charge separated (CS) states. Moreover, they can be significantly weakened by an external-electric field, which enhanced the yield of CT and CS states but attenuated the emission of the device. This study highlights that excessive LE-CT hybridization due to very low, whilst enabling direct and ultrafast charge transfer and increasing the proportion of radiative versus non-radiative recombination rates, comes at the expense of accelerating recombination losses competing with exciton-to-charge conversion process, resulting in a loss of photocurrent generation.

Original languageEnglish (US)
Article number2301026
JournalAdvanced Energy Materials
Volume13
Issue number32
DOIs
StatePublished - Aug 25 2023
Externally publishedYes

Keywords

  • charge generation
  • hybridization
  • non-radiative voltage loss
  • organic solar cells

ASJC Scopus subject areas

  • Renewable Energy, Sustainability and the Environment
  • General Materials Science

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