NOVELTY - A fluorescent material with an ultrahigh quantum yield, comprises: inorganic substrate material and lanthanide ions containing ytterbium ions Yb3+, where the ions Yb3+ doped the inorganic substrate material in the form of cluster; on the basis of the 100% total molar concentration of all positive metal ions, the Yb3+ ion has a molar concentration of 0.01-20%; and the ions Yb3+ form 3, 4 or greater than or equal to 5 clusters.    USE - As fluorescent material with an ultrahigh quantum yield; for increasing the photoelectric conversion efficiency of the solar battery, decreasing the ultraviolet irradiation intensity and reducing the heat loss of the photovoltaic cell (claimed).    ADVANTAGE - The fluorescent material can be applied to improve photoelectric conversion efficiency of solar cells, and reduce ultraviolet irradiation intensity and photovoltaic cell heat loss.    DETAILED DESCRIPTION - A fluorescent material with an ultrahigh quantum yield, comprises: inorganic substrate material and lanthanide ions containing ytterbium ions Yb3+, where the ions Yb3+ doped the inorganic substrate material in the form of cluster; on the basis of the 100% total molar concentration of all positive metal ions, the Yb3+ ion has a molar concentration of 0.01-20%; and the ions Yb3+ form 3, 4 or greater than or equal to 5 clusters. The Yb3+ ion cluster is covered or modified with at least one calcium difluoride (CaF2), silica (SiO2), calcium oxide (CaO), yttrium oxide (Y2O3), phospholipid, a surface active agent, and a polymer, in order to form fluorescent particles with a core-shell structure. The Yb3+ ion cluster is covered or modified with at least one titanium dioxide (TiO2), zinc oxide (ZnO), gallium nitride (GaN) or boron nitride (BN). The Yb3+ ion cluster is covered or modified with at least one benzophenone, phenyl triazine, benzotriazole, oxanilide, and methyl salicylate. The gadolinium (Gd)3+, thulium (Tm)3+, erbium (Er)3+, neodymium (Nd)3+, holmium (Ho)3+, europium (Eu)3+, Samarium (Sm)2+, or Yb2+ serves as the sensitizer ion or activator ion co-doped around the Yb3+ ion cluster.