Dependence of Interfacial Charge Transfer on Bifunctional Aromatic Molecular Linkers in CdSe Quantum Dot Sensitized TiO2 Photoelectrodes

Abstract

Quantum dot (QD) sensitization of TiO2 is a powerful method to improve its performance as a photoanode material in solar energy conversion. The efficiency of sensitization depends strongly on the rate of interfacial electron transfer (ET) from the QDs to TiO2. To understand the key factors affecting the ET, arene-substituted (ortho, meta, and para) bifunctional linkers with single or double aromatic rings were employed to link CdSe QDs to TiO2 and control the strength of their interaction as well as the rate of interfacial ET. Interestingly, the para-substituted aromatic linker, 4-mercaptobenzoic acid (4MBA) with the longest distance between the carboxyl and thiol groups, shows the best photoelectrochemical (PEC) performance, when compared to those of ortho-subtituted (2-mercaptobenzoic acid, 2MBA) and meta-substituted (3-mercaptobenzoic acid, 3MBA) aromatic linkers. Two other bifunctional linkers with double aromatic rings, 4′-mercapto-[1,1′-biphenyl]-4-carboxylic acid (4M1B4A) and 6-mercapto-2-naphthioc...