SYNTHESIS OF LUMINESCENT THIN-FILM CDSE ZNSE QUANTUM-DOT COMPOSITES USING CDSE QUANTUM DOTS PASSIVATED WITH AN OVERLAYER OF ZNSE/

Electronic and chemical passivation of CdSe nanocrystals (quantum dots ) has been achieved with a thin ZnSe overlayer grown in solution from trioctylphosphine selenide and diethylzinc. Layered particles with a [ ZnSe/CdSe] ratio ranging from 0 to similar to 5.0 were prepared and ch aracterized by optical absorption spectroscopy, photoluminescence, hig h-resolution transmission electron microscopy, Auger electron spectros copy, and X-ray scattering. The overgrown particles were crystalline a nd displayed band-edge absorption and emission characteristic of the i nitial CdSe nuclei. Thin-film quantum dot composites incorporating bar e and overcoated CdSe nanocrystals in a ZnSe matrix were synthesized b y electrospray organometallic chemical vapor deposition (ES-OMCVD). Th e photoluminescence spectra of the composites with bare CdSe dots were dominated by broad deep-level emission and the photoluminescence yiel d deteriorated with increasing deposition temperature. In contrast, th e composites incorporating the overcoated dots showed sharp band-edge emission. The presence of a preformed ZnSe layer resulted in a dramati c enhancement of the band-edge photoluminescence yield (by 2 orders of magnitude). The photoluminescence properties of composites with the p assivated dots were insensitive to deposition temperature over the ran ge studied.