AGBR PHOTOPHYSICS FROM OPTICAL STUDIES OF QUANTUM CONFINED CRYSTALS

Luminescence spectroscopy of nanocrystals (< 100 nm) has been used to probe the details of the low-temperature photophysics of AgBr, an indirect-gap semiconductor. Small crystallite size, moderate excitation levels, and radiative decay rates create a situation in which only one electron-hole pair exists in a given nanocrystal. These restrictions eliminate some of the decay channels and simplify the exciton emission spectrum for almost-equal-to 50-nm edge-length crystals. The exciton recombination in 10-nm-diam crystals dominates the emission spectrum. This emission is > 10(4) times as intense as exciton emission from a macroscopic crystal. Symmetry relaxation, carrier confinement, and impurity exclusion explain this increase in exciton emission. Doping experiments confirm the assignment of one set of exciton lines (BX8) as recombination emission from an exciton bound to an ionized donor.