Phthlocyanines are candidate building blocks for organic photovoltaic (OPV) devices. Crucial to the performance of OPV devices is the charge-injection barrier between the indium tin oxide (ITO) electrode and the organic semiconductor that arises from poor wettability of ITO surface towards the organic layer. Phosphonic acid (PA)-linked Pcs are an excellent candidate in this context because of the strong affinity of PAs towards ITO. Here monolayer films of zinc phthalocyanine (ZnPc-PA), tethered to ITO via the PA moiety, were characterized by polarized attenuated total reflectance (ATR) spectroscopy. The monomeric form of ZnPc-PA exhibit a more flat orientation, whereas the aggregated form of ZnPc-PA is oriented in a more upright arrangement. The electron transfer rate constants across the monolayer-ITO interface are measured using potential modulated attenuated total reflectance (PM-ATR) in TE and TM polarizations. This allows rate constants to be determined for sub-populations of molecules that are oriented predominately in-plane (monomers) and out-of-plane (aggregates), respectively.
ASJC Scopus subject areas
- Chemical Engineering(all)