Optical, electronic, and structural properties of uncoupled and close-packed arrays of InP quantum dots

Solid films consisting of close-packed arrays of InP quantum dots have been prepared by slowly evaporating colloidal solutions of InP quantum dots. Th e diameters of the quantum dots were controlled to be between about 30 to 6 0 Angstrom; size-selective precipitation yielded a size distribution of abo ut 10% about the mean diameter. The arrays show regions of hexagonal order, as well as disordered regions. Oxide layers can form irreversibly on the q uantum dot surface and limit the effectiveness of the size-selective precip itation. Photoluminescence spectra obtained from close-packed films of InP quantum dots formed from quantum dots with a single mean diameter and from a mixture of two quantum dot sizes show that energy transfer occurs from th e photoexcited smaller quantum dots to the larger quantum dots. The efficie ncy of this energy transfer process is high.