Photovoltaic Properties of Thin Films Based on a Composite of PbS Quantum Dots and a Fullerene Derivative: A Complex Ester of Butyric Acid

A study is made of the effect a surface ligand’s molecules have on the photoconductivity and photovoltaic effect in thin solid layers of structures based on PbS quantum dots. Thin solid layers are prepared of both quantum dots and bulk heterojunctions of a blend of quantum dots and fullerene derivative ([6,6]-phenyl-C(61)butyric acid ester (PCBM)). An exponential dependence of photoconductivity on the length of ligands is obtained for the quantum dot films, and the photovoltaic effect displays a strong dependence on the length of a ligand. In contrast, the effect the length of a ligand has on current–voltage characteristics and charge carrier mobility was not observed in bulk heterojunction structures with quantum dots. Physical reasons for the observed phenomena are discussed.