Understanding degradation pathways in organic photovoltaic cells (OPV) is essential to achieve long term device stability and allow commercialisation. Upon exposure to ambient atmosphere the power conversion efficiency (PCE) of PTB7:PC71BM solar cells, cast using the solvent additive DIO, is markedly reduced. Using electrically detected magnetic resonance (EDMR) spectroscopy trap sites, that form when the blend is exposed to air and DIO, are identified. Spin-Rabi oscillations reveal that the resonance arises from a weakly coupled pair of spin ½ species, while selective injection of charge carriers into the cell demonstrates that the spin-pair corresponds to recombination of electrons and holes. The recombination is assigned to holes on the PTB7 recombining with electrons localised to oxygen induced PC71BM trap sites.
|Number of pages||10|
|Journal||Journal of Materials Chemistry A: Materials for Energy and Sustainability|
|Early online date||12 Oct 2017|
|Publication status||Published - 7 Nov 2017|
- organic electronics
- photovltaic devices
- conjugated polymers