Surface Modification of CdSe Quantum Dots/Titanium Dioxide Heterostructures by Conjugated Organic Ligands

Abstract

Improving the charge transfer of quantum dots and the electron transport layer can greatly improve the efficiency of quantum dot sensitized solar cells (QDSSC). In this work, we used the ligand exchange method to improve the electron transfer efficiency between CdSe QDs and electron transport layer. The short chain-ligand containing disulfide bond and benzene ring conjugated structure was selected as the surface ligand of CdSe QDs. Because of its unique disulfide bond and conjugated structure, the stability and electron transfer efficiency of QDs in TiO2 layer can be effectively improved. The surface ligand has good stability and the ability to promote charge transfer, which can effectively improve the efficiency of QDSSC. By characterizing of fluorescence performance and the analysis of fluorescence lifetime, the surface of this ligand behaves fluorescence quenching phenomenon and life decay phenomenon after modification. Furthermore, photovoltaic devices constructed by the as-prepared dithiocarbamate functionalization of CdSe@TiO2 have also been assembled with the highest PCE of 5.22%.