Probing charge transfer states at organic and hybrid internal interfaces by photothermal deflection spectroscopy

Research output: Contribution to journalResearch articleContributedpeer-review

Contributors

  • David Becker-Koch - , Heidelberg University  (Author)
  • Boris Rivkin - , Heidelberg University  (Author)
  • Fabian Paulus - , Heidelberg University  (Author)
  • Hengyang Xiang - , Sorbonne Université (Author)
  • Yifan Dong - , Imperial College London (Author)
  • Zhuoying Chen - , Sorbonne Université (Author)
  • Artem A. Bakulin - , Imperial College London (Author)
  • Yana Vaynzof - , Heidelberg University  (Author)

Abstract

In organic and hybrid photovoltaic devices, the asymmetry required for charge separation necessitates the use of a donor and an acceptor material, resulting in the formation of internal interfaces in the device active layer. While the core objective of these interfaces is to facilitate charge separation, bound states between electrons and holes may form across them, resulting in a loss mechanism that diminishes the performance of the solar cells. These interfacial transitions appear in organic systems as charge transfer (CT) states and as bound charge pairs (BCP) in hybrid systems. Despite being similar, the latter are far less investigated. Herein, we employ photothermal deflection spectroscopy and pump-push-probe experiments in order to determine the characteristics and dynamics of interfacial states in two model systems: an organic P3HT:PCBM and hybrid P3HT:ZnO photovoltaic layer. By controlling the area of the internal interface, we identify CT states between 1.4 eV and 1.8 eV in the organic bulk-heterojunction (BHJ) and BCP between 1.1 eV and 1.4 eV in the hybrid BHJ. The energetic distribution of these states suggests that they not only contribute to losses in photocurrent, but also significantly limit the possible maximum open circuit voltage obtainable from these devices.

Details

Original languageEnglish
Article number124001
JournalJournal of Physics Condensed Matter
Volume31
Issue number12
Publication statusPublished - 30 Jan 2019
Peer-reviewedYes
Externally publishedYes

External IDs

PubMed 30572317

Keywords

Sustainable Development Goals

Keywords

  • bound charge pair states, charge transfer states, hybrid organic-inorganic interfaces, organic interfaces, photothermal deflection spectroscopy

Library keywords