Boosting, Probing and Switching-Off Visible Light-Induced Photocurrents in Eumelanin-Porous Silicon Hybrids

A relatively intense photocurrent density up to 3.8 mA/cm2 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.