PbSe Nanorods for Hybrid Solar Cells: Optimization of Synthesis Protocols and Investigation of Surface Stability

摘要

Multiple Exciton Generation (MEG) concept has been reported to be one of the most effective method to exceed 33% Shockley-Queisser theoretical limit. According to the recent reports, 2-D nanostructures are better alternative for MEG compared to dots. We therefore report optimized lead selenide nanorod (PbSe NRs) synthesis conditions, known to have the highest MEG yield, to reach the best performing synthesis protocol and investigate the stability of NRs against air and moisture. We found that reaction parameters such as temperature profile, oleic acid to lead ratio (OA/Pb) and the presence of catalyst have significant effects on the optical and morphological properties of the NRs. The transformation of dots to rods starts when the OA/Pb ratio increases from 1.5 to 3.5 together with an increase in both branching and length of the rods. Utilizing catalyst to improve the NR yield requires careful optimization as the unoptimized concentration of catalyst leads to the breakage of rods to dots as the reaction proceeds. We also report high sensitivity of PbSe NRs towards oxidation. Surface, being the main suspect of the degradation, plays a crucial role as oxidation starts from the surface and proceeds towards the core.