The uses of solar energy instead of fossil fuels to supply the global energy demand demonstrate the importance of developing solar cells. Among all solar cells, colloidal quantum dot solar cells have attracted particular attention due to their easy fabrication, size control, low cost, and flexibility. The depleted heterostructure solar cell is introduced and simulated using quantum dots of CdS and TiO₂ layers. Then, the Schrödinger equation is solved in the spherical polar coordinate and using the obtained eigenfunctions and eigenvalues, the absorption coefficient of other structural parameters are obtained by finite-difference time-domain method. Then solving Maxwell and Poisson equations using the electric field emitted from sunlight radiation, the generation rates of carriers and the current density and other characteristics of the solar cell based on introduced structure are obtained. For studied structures, the obtained optimum results are J_sc  ≈  15  mA  /  cm² and η  ≈  7  %  . The obtained values are relatively good in comparison with the experimental results for similar materials.