ENGINEERING OF GOLD SURFACE WORK FUNCTION BY ELECTRODEPOSITION OF SPIROBIFLUORENE-BASED DONOR-ACCEPTOR BIPOLAR SYSTEMS

L FERNANDEZ, PHILIPP ZABEL, THOMAS DITTRICH, YUAN-LI LIAO, CHI-YEN LIN, KENTSUNG WONG, FERNANDO FUNGO AND LUIS OTERO

La Plata

Congreso; 4º Encuentro de Física y Química de superficies; 2009

Interfaces between metal s and organic materials are crucial for electronic properties and char2eseparation in devices such as organic light emitting diodes; organic field effect transistoíS:electrochromic systems and organic solar cells. The efficiency of these heterojunction devicesstrongly depends on the charge injection process (of holes or electrons) between the meta:electrodes and the active organic layers. Metal/organic material interface is one of the deviceparameters that more attention has attracted in the search of improvement devices performance,because the formation of the metal/organic junction leads to modification in important properties.such as metal work function and orbital energy of the organic layer.In this work, charge separation in gold/spirobifluorene-based donor (triphenylamine)-acceptor(cyano) bipolar systems has been investigated by contact potential difference and surfacephotovoltage´ spectroscopy. Organic films were formed on gold electrode by electrochemicalpolymerization and by dipping in dye solution. The gold surface work function has been changedover more than 0.4 V depending on the numbers of electrochemical deposition cyc1es. Photovoltageeffects were analyzed in terms of internal photoemission from Au into organic film, and organiclayer light absorption. The energetic differences between the Fermi-level of Au and HOMO levels of organic systems were obtained. The results showed that the electrodeposition is a versatile tool for electro de surface work function tuning.