Photovoltaic properties of PSi impregnated with eumelanin

Abstract

A bulk heterojunction of porous silicon and eumelanin, where the columnar pores of porous silicon are filled with eumelanin, is proposed as a new organic-inorganic hybrid material for photovoltaic applications. The addition of eumelanin, whose absorption in the near infrared region is significantly higher than porous silicon, should greatly enhance the light absorption capabilities of the empty porous silicon matrix, which are very low in the low energy side of the visible spectral range (from about 600 nm downwards). The experimental results show that indeed the photocarrier collection efficiency at longer wavelengths in eumelanin-impregnated samples is clearly higher with respect to empty porous silicon matrices.

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

“…This is analogous to that already observed in [47] for PSi and PSi with eumelanin. Fringes displacement demonstrates that, as in the case of the DHI impregnation, there is a modification of the average refractive index of the porous layer that, in this case, can be easily attributed to a modification of the pores content, due to conversion of DHI to eumelanin.…”

“…In the preceding paper [47], photocurrent densities in the order of 5 μA/cm 2 were measured upon exposure to visible light of a PSi--eumelanin hybrid obtained by oxidizing DHI (50 mmol) in phosphate buffer, 0.1 M, pH 7.4, with tyrosinase under a stream of oxygen. Immobilization on PSi was obtained by treating the substrate with the appropriate solution/suspension of DHI or synthetic melanin in methanol, methanol/water, or methanol/phosphate buffer pH 7.0 as the media.…”

“…Immobilization on PSi was obtained by treating the substrate with the appropriate solution/suspension of DHI or synthetic melanin in methanol, methanol/water, or methanol/phosphate buffer pH 7.0 as the media. The optical properties of the hybrids were investigated by optical reflectivity measurements performed on both untreated and impregnated PSi matrices (a detailed description of the technique and the spectra has been given previously [47] ). In this study, eumelanin film synthesis was carried out with the recently developed AISSP methodology which circumvents issues relating to eumelanin insolubility by allowing in--situ deposition on the inorganic substrate of dark smooth DHI melanin films with improved structural [21].…”

“…However, very few studies have dealt with its photovoltaic properties [39--41], since most silicon--based organic hybrids thus far considered [43] were constructed on amorphous [44] or crystalline [45] Si. Recently [47], we demonstrated that PSi impregnated with synthetic DHI eumelanin exhibits a photoresponse at λ > 500 nm of potential relevance for solar cells, although the measured photocurrent densities were relatively low (ca. Recently [47], we demonstrated that PSi impregnated with synthetic DHI eumelanin exhibits a photoresponse at λ > 500 nm of potential relevance for solar cells, although the measured photocurrent densities were relatively low (ca.…”

Melanins and melanogenesis: from pigment cells to human health and technological applications

“…prepared an intercalated hybrid material by reacting DOPA with a V 2 O 5 nH 2 O gel preserving the lamellar structure of V 2 O 5 and demonstrating the reduction of V(V) to V(IV) ions with associated stability of the V 2 O 5 electrochromic response and conductivity (Oliveira et al., ). Recently, a bulk heterojunction of porous silicon and eumelanin was obtained, featuring an increased photocarrier collection efficiency at longer wavelengths with respect to bare porous silicon matrices (Mula et al., ). Qu et al.…”