Tuning and Enhancing White Light Emission of II-VI Based Inorganic-Organic Hybrid Semiconductors as Single-Phased Phosphors

Single-phased white light emitters made of semiconductor bulk materials are most desirable for use in white light-emitting diodes (WLEDs) based on both photoluminescence and electroluminescence. Here we demonstrate Cd and/or Se substituted double-layer [Zn2S2(ha)] (ha = n-hexylamine) hybrid semiconductors emit bright white light in the bulk form and their emission properties are systematically tunable. The ternary Zn2-2xCd2xS2(ha) hybrid compounds exhibit two photoluminescence (PL) emission peaks, one of which being attributed to band gap emission, and the other resulting from Cd doping and surface sites. The Cd concentration modulates the optical absorption edge (band gap) and the positions of the two emission bands along with their relative intensities. The ZnS-based hybrid structures (with a nominal Cd mole fraction x = 0.25) emit bright white light with significantly enhanced photoluminescence quantum yield (PLQY) compared to its CdS-based hybrid analogues. For the quaternary Zn2-2xCd2xS2-2ySe2y(ha) compounds (x = 0.25 and different nominal Se mole fractions y) the synergetic effect between doped Cd and Se atoms leads to further tunability in the band gap and emission spectra, yielding well balanced white light of high quantum yield. Detailed analysis reveals that the PL emission properties of the ternary and quaternary hybrid semiconductors originate from their unique double-layered nanostructures that combine the strong quantum confinement effect and large number of surface sites. The white-light emitting hybrid semiconductors represent a new type of single-phased phosphors with great promise for use in WLEDs.