Engineering of gold surface work function by electrodeposition of spirobifluorene donor–acceptor bipolar systems

Charge separation in gold/spirobifluorene-based donor (triphenylamine)–acceptor (cyano) bipolar systems has been investigated by contact potential difference and surface photovoltage spectroscopy. Organic films were formed on gold electrode by electrochemical polymerization and by dipping in dye solution. The gold surface work function has been changed over more than 0.4 eV depending on the numbers of electrochemical deposition cycles. Photovoltage effects were analyzed in terms of internal photoemission from Au into organic film, and organic layer 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 electrode surface work function tuning.