Why holes and electrons separate so well in polymer/fullerene photovoltaic cells

David P. McMahon, David Cheung, Alessandro Troisi

Research output: Contribution to journalArticlepeer-review

177 Citations (Scopus)


The electronic and geometric structure of a prototypical polymer/fullerene interface used in photovoltaic cells (P3HT/PCBM) is investigated theoretically using a combination of classical and quantum simulation methods. It is shown that the electronic structure of P3HT in contact with PCBM is significantly altered compared to bulk P3HT. Due to the additional free volume of the interface, P3HT chains close to PCBM are more disordered, and consequently, they are characterized by an increased band gap. Excitons and holes are therefore repelled by the interface. This provides a possible explanation of the low recombination efficiency and supports the direct formation of “quasi-free” charge-separated species at the interface.
Original languageEnglish
Pages (from-to)2737–2741
Number of pages5
JournalJournal of Physical Chemistry Letters
Issue number21
Publication statusPublished - 12 Oct 2011


  • organic solar cells
  • electron transfer
  • molecular dynamics
  • disorder


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