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DS: Fachverband Dünne Schichten

DS 23: Focussed Session: Inorganic/Organic Semiconductor Hybrid Structures II (jointly with HL and O)

DS 23.1: Hauptvortrag

Dienstag, 15. März 2011, 14:15–14:45, POT 151

Interfacial charge-carrier energetics probed by electromodulated absorption spectroscopy: implication for organic-inorganic hybrid photovoltaic devices — •Peter Ho — Dept of Physics, National University of Singapore

The transition from vacuum-level alignment to Fermi-level pinning of the organic semiconductor contact as the work function of the "metallic" electrode crosses a certain threshold value has been well-established by numerous careful ultraviolet photoemission spectroscopy stuides. In this talk, I will discuss the use of electromodulated absorption spectroscopy to probe this transition within the devices directly through the built-in potential measured at the Stark feature, and also the interface polaron density measured in the subgap. Therefore the results are particularly relevant to the operation of light-emitting diodes and photovoltaic cells. We found that the pinning crossover occurs surprisingly at different work-function threshold values. The implications of this result for energy-level alignment and contact optimisation in light-emitting diodes and photovoltaic devices, and in hybrid inorganic-organic semiconductor photovoltaic devices, will also be discussed.