To comprehensively assess the impact of these structures on photoelectric emission performance， we design and cultivate photocathode samples featuring both configurations， subsequently comparing their photoemission performance. Optical properties and the quantum efficiency model are ascertained through the matrix method of thin-film optics and one-dimensional continuity equations， respectively. We examine and analyze the effects of varying the thickness of the emission layer， altering the buffer layer， and adjusting the Al component within the buffer layer on the optical properties and quantum efficiencies of these two photocathode structures via simulations. These two structures exert distinct influences on photoelectric emission performance due to their disparate mechanisms. Consequently， their effects on photoemission performance exhibit substantial differences. The photocathode with the graded bandgap structure improves the photoelectric emission performance by introducing a built-in electric field and reducing interface recombination. Conversely， the DBR structure augments the photoelectric emission by forming a Fabry Robb resonant cavity， so that incident light of a specific wavelength can be reflected back and forth in the resonant cavity and absorbed many times. The results of an activation experiment indicate that the emission efficiency of DBR structures exceeds that of graded bandgap structures. Notably， higher emission efficiency peak values are obtained at the wavelengths of 755， 808， and 880 nm， which can be improved by 37.5%， 38.9%， and 47.0%， respectively. Furthermore， the quantum efficiency curves are well fitted using the derived model， confirming the importance of optical performance parameters and the model’s validity.