The main objective of this work is to do a comparative study of the spectral responses of three models: homojunction CuInSe2 with CdS window layer (CdS (n) / CuInSe2 (n) / CuInSe2 (p)), homojunction CuInSe2 deposited on CdTe substrate (CuInSe2 (n) / CuInSe2 (p) / CdTe (p)) and homojunction CuInSe2 with a window layer (CdS) and deposited on a CdTe substrate (P) / CdTe (p) :CdS (n) / CuInSe2 (n) CuInSe2 (p)/CdTe (p). We calculated the expressions of these respective spectral responses by solving the continuity equations governing the variation of the minority carriers in each region for each model and using the appropriate boundary conditions. We made a simulation of intern quantum efficiency according to the energy of the photons while preserving the same values of geometrical parameters .The results show that the homojunction with window and deposited on a substrate (CdS (n) / CuInSe2 (n) CuInSe2 (p) / CdTe (p) gives the best internal quantum efficiency. The window layer reduces the losses at the surface at the window-emitter interface. The substrate increases the collection of the carriers in the base. After choosing the best model, we studied the influence of geometrical and electrical parameters on the spectral response. We have also seen that the best spectral response is obtained with a small thickness of the emitter, a diffusion length of the holes and electrons respectively greater than the thickness of the buffer layer and the absorbing layer.