Generation of Surface Photovoltage at Porphyrin Polymer/C60 Interfaces

JAVIER DURANTINI, MATIAS FUNES, EDGARDO DURANTINI, LUIS OTERO, MARISA SANTO, THOMAS DITTRICH, MIGUEL GERVALDO.

Mendoza

Conferencia; 21th IAPS conference; 2011

Interfaces between semiconductors and organic polymers are crucial for electronic properties and charge separation in devices such as organic light emitting diodes; organic field effect transistors; electrochromic systems and organic solar cells. These applications are closely related to the behavior of photogenerated charge carriers. Obviously, it is valuable to investigate the surface photovoltage properties of these organic polymers since such investigation gives us much information about the photogenerated charge carriers at semiconductors’ surface or interface, electron transfer and charge separation effect. On the other hand many studies on the development of organic optoelectronics incorporate chlorophyll derivatives and several analogues of natural pigments, such as porphyrins and phthalocyanine compounds, as light receptors and charge storage units. Donor-acceptor systems can be constructed using porphyrins and C60 Buckminsterfullerene, opening up the possibility of constructing artificial photosynthetic systems in which there is a photoinduced electron or energy transfer process from a chromophore donor to a fullerene acceptor. Furthermore, it is possible to modify the porphyrin ring whit substituents with the capacity to form electropolymerized films over conducting surfaces. The electrochemical polymerization permits fine control over thickness and polymer properties; allowing to obtain stable and reproducible organic films.In this work we report the surface photovoltage spectroscopy (SPV) of two novel porphyrin electropolymerized films. SPV is a contactless technique for characterization of semiconductors and semiconductor interfaces and the measurements are based on monitoring illumination-induced changes in the surface potential as a function of incident photon energy. The new porphyrin polymer films deposited on ITO show photovoltages in visible region which match the film absorption spectra. Deposition of an additional C60 layer on top of the porphyrin films shows an increase in the SPV values, showing the efficiency of these donor-acceptor systems.