Enhanced Surface Passivation of Colloidal CdSe Nanocrystals for Improved Efficiency of Nanocrystal/Polymer Hybrid Solar Cells

We report on a highly effective surface passivation ligand, i.e., thiophenol (TP), for cadmium selenide (CdSe) colloidal nanocrystals (NCs) to improve the performance of CdSe NCs:MEH-PPV hybrid solar cells (HSCs). Post-TP surface treatment of CdSe NCs produces enhanced surface passivation of the high density of NC surface states, resulting in greatly increased photocurrent generation from the NCs, and boosts the overall device performances. The power conversion efficiency of the HSCs with TP surface ligand is improved to 1.57% from 0.32% of a conventional ligand, i.e., pyridine, treated device made with only 10-mg/ml low concentration of NCs, which was blended with polymer at 1:6 (NC:polymer) ratio.