Deciphering Molecular Mechanisms of Interface Buildup and Stability in Porous Si/Eumelanin Hybrids

Abstract

Porous Si/eumelanin hybrids are a novel class of organic–inorganic hybrid materials that hold considerable promise for photovoltaic applications. Current progress toward device setup is, however, hindered by photocurrent stability issues, which require a detailed understanding of the mechanisms underlying the buildup and consolidation of the eumelanin–silicon interface. Herein we report an integrated experimental and computational study aimed at probing interface stability via surface modification and eumelanin manipulation, and at modeling the organic–inorganic interface via formation of a 5,6-dihydroxyindole (DHI) tetramer and its adhesion to silicon. The results indicated that mild silicon oxidation increases photocurrent stability via enhancement of the DHI–surface interaction, and that higher oxidation states in DHI oligomers create more favorable conditions for the efficient adhesion of growing eumelanin.

Eumelanin Adsorption on Silicon: Optical Properties of Si(001)-Adsorbed Eumelanin Tetrameric Protomolecules

“…Indeed the ability of eumelanin functionalization to extend the absorption range of PSi towards longer wavelengths has been demonstrated. 1,2 The basic building blocks of eumelanin are 5,6-dihydroxyindole (DHI) -like molecules.…”

Physical and Chemical Control of Interface Stability in Porous Si–Eumelanin Hybrids

“…29 In our previous proof-of-concept investigations we reported PSi/eumelanin nanocomposites for photovoltaic applications and demonstrated the ability of eumelanin functionalization to enhance substrate photoconductivity. 25,31 However, despite the improved photoconductivity produced by eumelanin functionalization, the reduced photocurrent stability over days limits the ability to accomplish steps forward toward technology transfer. 31 Apparently, the stability issues stem from the characteristics of the PSi/eumelanin hybrid, including chiefly the buildup of the polymer within the pores in relation to the nature and shape of the inorganic material (irregular dendritic pores are present in the case of PSi).…”

Melanin-Based Functional Materials

“…Future advancements in the development of melanin-based functional materials are expected to greatly benefit from the rational design of hybrid organic-inorganic systems and from a thorough understanding of the fundamental interaction mechanisms at the interface. In this Special Issue, Pinna et al, reported a combined experimental and computational investigation aimed at modeling the melanin-porous silicon interface and at elucidating the factors controlling its stability [ 9 ]. The results showed that oxidation of the inorganic surface and the oligomer components improves adhesion and enhances photocurrent stability.…”