Colloidal synthesis and electroluminescence properties of nanoporous MnIIZnS films

An organometallic colloidal route was employed to prepare orange fluorescing Mn2+ functionalized ZnS and CdS particles, For this purpose, tributylphosphine-capped manganese oxide clusters were first synthesized, which served as heterogeneous nucleation centers in the ZnS condensation process. An exposure of the resulting Mn:ZnS particles to Cd2+ initiates a metal replacement yielding Mn:CdS. This process broadens the characteristic internal Mn2+-emission band peaking at 600 nm and enhances the fluorescence quantum yield from 3% to 6%. The size of the metal sulfide particles was determined to be 3-4 nm using HRTEM and XRD measurements. The colloids were further used to prepare thin, crack-free layers placed between ITO and Al contact electrodes, which allowed us to investigate their electroluminescence properties. We have found that an infiltration of ZnI2 or other molecular cluster species dramatically improves the air stability and efficiency of the Fl, device. The most efficient samples have shown a luminance of about 10 cd/m(2) at 100 mA/cm(2) and 9 V. The corresponding EL efficiency was about 0.001%. Current-voltage data collected on the EL-test components indicate a mobility controlled transport of the injected charge carriers. Finally, an energy level scheme is proposed to describe the excitation mechanism of the electroluminescence in the Mn2+-containing inorganic-organic nanostructures.