Synthesis and thermal annealing treatment of octylphosphonic acid-capped CdSe-tetrapod nanocrystals for bulk hetero-junction solar cell applications

Abstract

CdSe-tetrapod nanocrystals (NCs) were synthesized by using octylphosphonic acid (OPA) as a capping ligand and cadmium oxide (CdO) as a cadmium precursor. The effects of thermal annealing in nitrogen (N2) environment on the chemical composition, morphology, crystal structure and optoelectronic properties of the CdSe-tetrapods have been investigated. Remarkable difference in the morphological and optoelectronic properties between as-synthesized and N2-annealed CdSe NCs was observed. The photoluminescence (PL) peak of N2-annealed CdSe NCs shifted to lower energy and UV-vis absorption spectra shifted to longer wavelength, indicating the size increase and improvement of the crystallinity of the CdSe tetrapods. The power conversion efficiency of bulk hetero-junction solar cells made with the annealed CdSe NCs showed higher value compared with the efficiency of cells made with as-synthesized CdSe NCs.