Up-conversion infrared (IR) photodetectors show great potential in large-array and low dark current IR detection due to the advantages of pixelless imaging and being free from thermal mismatch between photodetectors and read-out integrated circuits. The emission efficiency of near-IR photons is one of the important issues that influence the up-conversion efficiency. In this paper, cascade IR up-converters with different numbers of emission quantum wells were designed and fabricated. Based on the IR response measurement and simulation of carrier distribution, the influence of the number of quantum wells on the emission efficiency of near-IR photons was investigated. The experiment results indicate that the near-IR emission efficiency can be improved by adopting single emission quantum well, which consequently improves the up-conversion efficiency.