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Phosphorescent metal complexes exhibit extensive applications in material science,biological field,display and lighting etc.Luminescent materials are the most crucial elements in organic light-emitting diodes(OLEDs).Since metal-coordinated phosphors harvest both singlet and triplet excitons in the devices,the energy can be fully utilized to achieve high-efficiency electroluminescence.Compared with phosphorescent mononuclear metal complexes,the oligonuclear complexes exhibit several advantages as phosphorescent emitters in OLEDs,including more facile intersystem crossing,better molecular rigidity,and more avenues for tuning emissive character through ligand modification and structural modulation.We have launched recently a project for the design of heteronuclear metal cluster complexes to attain high-efficiency OLEDs through solution process.The photoluminescence/electroluminescence is systematically modulated by elaborately design of polyphosphine-supported d8-d10 and d10-d10 metal cluster complexes with various nuclearities,changing metal ions and modifying bridging and ancillary ligands.The solution-processed OLEDs exhibit high-efficiency electroluminescence with the highest current efficiency close to 80 cd A-1 and external quantum efficiency(EQE)over 21%.This represents one of the best performances for solution-processed OLEDs,which is comparable to the state-of-the-art phosphorescent OLEDs based on mononuclear cyclometallated iridium(Ⅲ)complexes.It is revealed that the use of hole-transport and electron-transport ligands to fabricate phosphorescent metal cluster structures is beneficial to achieve superior electroluminescent performance.