A Non-Oxidative Approach Towards Hybrid Silicon Nanowire- Based Solar Cell Heterojunctions

Abstract

A general method for the non-oxidative termination of silicon nanowires (Si NWs) is reviewed. Oxide-free Si NW have been successfully alkylated in the lab using a two-step chlorination/alkylation process. The distinctive properties of the resulting Si NW have been taken advantage of by integrating the Si NWs into functional devices such as solar cells. Moreover, molecularly terminated Si NWs exhibit lower defect density emissions than unmodified Si NWs. This, in part, explains the better performance of the molecularly terminated Si NW- based solar cells. Solar cells that use organic-inorganic hybrid Si NWs as absorbers show an increased open-circuit voltage (Voc), an increased short- circuit current (Jsc) and a higher fill factor (FF). The aim of chemical functionalization is to protect Si NWs from extensive oxidation, add functionality and to adjust surface electronic properties such as the work function, surface Fermi level and band bending. The stability of the terminated of Si NWs was found to be dependent on the molecular chain length, molecular coverage, interaction type (π-π or σ-σ), surface energy and Si NW diameter.