Novel Eu2+,3+/Yb3+ co-doping calcium aluminosilicate glasses prepared under a vacuum atmosphere were developed and characterized from the spectroscopic point of view, as a potential spectral converter for application in solar cells. The emission of near-infrared photons by downconversion due to cooperative energy transfer (ET) from Eu2+ and Eu3+ to Yb3+ in these glasses was reported. Absorption, excitation, emission, and fluorescence decay measurements were performed to examine the ET processes. The occurrence of cooperative energy transfer from Eu2+ and/or Eu3+ to Yb3+ ions was discussed in detail. The obtained samples have high efficiency and broad absorption in the ultraviolet and visible regions. Under 325 nm excitation, the samples achieve intense near-infrared emission, which increases with Yb2O3 concentration (0 < Yb2O3 < 1.38 mol. %). The energy transfer efficiency from Eu2+,3+ to Yb3+ was evaluated, and a maximum efficiency of ∼85% was obtained (Yb2O3 = 1.38 mol. %).