Polymer wires with quantum dots grown by molecular layer deposition of three source molecules for sensitized photovoltaics

Abstract

Molecular layer deposition (MLD) can be used to grow organic tailored materials, where different molecules are sequentially connected in designated arrangements. Using MLD, polymer wires containing quantum dots (QDs) of lengths ∼0.8, ∼2, and ∼3 nm were grown by connecting three source molecules in monomolecular steps. The peak energy of the QD absorption shifted to higher energy with decreasing QD length, due to the quantum confinement effect. Consequently, the polymer wires exhibited a widening of their absorption spectra from ∼480 to ∼300 nm. This was attributed to the superposition of individual absorption bands of different QDs. A sensitization model for ZnO in photovoltaic devices is proposed, in which polymer wires with QDs as the sensitizing layer reduce the heat energy loss during absorption.