Boosting, probing and switching-off visible light-induced photocurrents in eumelanin-porous silicon hybrids

Abstract

A relatively intense photocurrent density up to 3.8 mA cm⁻² was induced by visible light in n⁺-doped porous silicon (n-PSi) coated with a eumelanin thin film produced by ammonia-induced solid state polymerization (AISSP) of 5,6-dihydroxyindole (DHI). The photocurrent was not affected by acetic acid vapors but was irreversibly abated by gaseous ammonia. No detectable photocurrent was observed using p⁺-PSi as the inorganic substrate. These results point to eumelanin as a powerful enhancer of PSi photoresponse to visible light via hole-type electrical conduction.