Effect of surface passivating ligand on structural and optoelectronic properties of polymer : CdSe quantum dot composites

Abstract

We demonstrate the effect of surface passivation of cadmium selenide quantum dots (CdSe QDs) (~5–7 nm) by tri-n-octylphosphene-oxide (TOPO) and oleic acid (OA) on the structural and optoelectronic properties of their respective polymer : CdSe composites by dispersing them in poly(2-methoxy-5(2-ethylhexyloxy)-1,4-phenylinevinylene) and poly(3-hexylthiophene) polymers. It has been found that OA passivated-QDs (~7 nm), as compared with TOPO passivated CdSe QDs (~5 nm), are of (i) high quality that provide better steric stability against coagulation, homogeneity and photostability to their respective polymer : CdSe composites, (ii) show low value of Stern–Volmer quenching constant (KSV) calculated from photoluminescence quenching measurements. These effects have been attributed to (i) CdSe(OA) (~7 nm) particles having relatively smaller surface energies compared with CdSe(TOPO) (~5 nm) particles thus showing lesser quenching capabilities (ii) dominance of respective processes of photoinduced Forster energy transfer between host polymer (donors) and guest CdSe nanocrystals (acceptors) in polymer : CdSe(OA) composites and charge transfer in polymer : CdSe(TOPO) composites.