In the photovoltaic field, research is focused on two important axes: increasing cell efficiency, and reducing fabrication costs. To reduce the cost of the base materials, it is necessary to reduce the thickness of the active layers. The basic idea is to make a layer of high structural and electronic quality silicon of small thickness (10–50 μm). This layer could be grown by epitaxial techniques on a low‐cost monocrystalline silicon substrate with an emitter formed by phosphorus diffusion. The silicon layer is characterized by a diffusion length comparable to its thickness, a value that can be expected for the epitaxial layers. This study aims to optimize the physical and technological performances of a crystalline silicon solar cell deposited by an epitaxial process on a low‐cost monocrystalline silicon substrate with large thicknesses since there is no reflector on the backside. This structure is characterized by the following parameters: (Thickness of the base layer XB = 56 μm, the efficiency η = 15.2%, the open‐circuit voltage Voc = 623 mV and the short‐circuit current Isc = 30 mA). The calculations were carried out by the PC1D software, aiming to find a new solar cell structure by keeping the same characteristic parameters mentioned above (η, Isc, and Voc) while decreasing the thickness of this solar cell. The effect of the different parameters on the performance of the solar cell was investigated. The obtained results showed that it is possible to reduce the substrate thickness from 56 to 30 μm while keeping the same characteristics parameters of the cell (η = 15.2%, Voc = 622.7 mV, Isc = 30.1 mA).