Study of the nanoscale surface photovoltage of organic semiconductors combining optical and Kelvin probe microscopy

DIPC Seminars

Elisa Palacios- Lidon CIOyN, Universidad de Murcia, Murcia, Spain
Donostia International Physics Center (DIPC).Paseo Manuel de Lardizabal, 4 (nearby the Facultad de Quimica), Donostia
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Study of the nanoscale surface photovoltage of organic semiconductors combining optical and Kelvin probe microscopy Elisa Palacios- Lidon CIOyN, Universidad de Murcia(Campus Espinardo), E-30100 Murcia (Spain) []( Nowadays, organic and molecular electronic has become a hot topic since devices based on this technology offer a cheap and versatile alternative to conventional silicon ones. The reliability of organic photodevices such as plastic solar cells and OLEDs lies on understanding and tuning their electro optical properties. In these systems, the relevant photo induced physico-chemical processes take place at the nanoscale and therefore, a deeper understanding of the correlation between structural optical and electronic properties at this scale will shed some light on the open questions about transport properties and degradation processes of these materials. To fulfil these requirements, in this work we will explore the capabilities of Kelvin Probe Microscopy technique (KPM) combined with traditional optical techniques applied to organic semiconductor thin films. We propose a novel measuring methodology together with an appropriated data analysis to study the temporal evolution of photo-physical and photo-chemical phenomena such as the mesoscale polymer electronic light induced response and polymer photo-degradation as well as the local nanoscale electro-optical properties. In addition, a correlation between changes in the surface photovoltage (SPV) and in the optical properties due to external illumination can be established. One example of the potential and versatility of this technique is the evolution of the SPV when it is irradiated. During illumination the SPV reach a maximum value and then, it decrease until no SPV effect is measured. The corresponding optical micrographs indicate that light induces photobleaching degrading the polymer. It has been found that the SPV characteristics strongly depend on the irradiation wavelength and on the irradiation intensity in a non-trivial way.