TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The quantum dot comprises at least one element comprising Group II-VI, Group Ill-V, Group IV-VI and Group IV semiconductors, preferably zinc oxide, zinc sulfide, zinc selenide, zinc telluride, cadmium sulfide, cadmium selenide, cadmium telluride, mercury sulfide, mercury selenide, mercury selenide, magnesium sulfide, magnesium selenide, germanium sulfide, germanium selenide, germanium selenide, tin sulfide, tin selenide, tin telluride, lead oxide, lead sulfide, lead selenide, laed telluride, gallium nitride, gallium phosphide, gallium arsenide, gallium antimony, indium nitride, indium phosphide, indium arsenide, indium antimony, aluminum nitride, aluminum nitride phosphide, aluminum arsenide, aluminum antimony, and an appropriate combination of two or more such semiconductors, and /or with core/shell, or its core multi-shell layered structures.    TECHNOLOGY FOCUS - INSTRUMENTATION AND TESTING - Preferred Components: The charge generation layer or hole injection layer has a working function or electron affinity higher than 5.6 eV, preferably 6.0 eV, where the hole injection layer or charge generation layer comprises at least one element of a transition metal oxide, vanadium oxide of formula (VOx), molybdenum oxide of formula (MoOx), ruthenium oxide of formula (RuOx) and tungsten oxide of formula (WOx). The ionization potential or the valence band of the quantum dot is at least 0.3 eV, preferably 0.5 eV higher than HOMO of the organic host, or the electron affinity or conduction band of the quantum dot is at least 0.3 eV, preferably 0.5 eV lower than the lowest unoccupied molecular orbital (LUMO) of the host material. The host material is at least one element comprising a host material having a bigger band gap than the quantum dot, an organic compound having a HOMO at least lower than -5.7 eV, and an organic compound having a LUMO at least lower than -3.0 eV. The quantum dot has a valence band higher than -5.7 eV, preferably higher than -5.3 eV. The concentration of the quantum dot is 0.5-30 (preferably 2-10) vol%, such that the quantum dot works as hole trap or electron trap in the organic host. The organic host has a bigger band gap than the quantum dot. The quantum dot has a valence band (VB) higher than -5.7 eV, preferably -5.3 eV. The organic host is at least one element of an organic compound having a HOMO at least lower than -6.0 eV, a small molecule and/or a polymer. The further emitter is organic compounds or other quantum dots. The hole transport unit comprises at least one group of small molecule hole transport material, an amine, a triarylamine, a thiophene, a carbazole, a phthalocyanine, a porphyrine, or its isomers and derivatives. (I) comprises the mixture or a quantum dot, or an anode, a cathode and a functional layer in-between the anode and the cathode, where the functional layer comprises the mixture, or the quantum dot. (I) or mixture comprises at least one further organic emitter, or at least one further organic emitter having an absorption spectrum overlapping with an emission spectrum of the quantum dot.x = not defined.