A bifacial silicon solar cell under monochromatic illumination in frequency modulation by the rear side is being studied for the optimization of base thickness. The density of photogenerated carriers in the base is obtained by resolution of the continuity equation, with the help of boundary conditions at the junction surface (n + /p) and the rear face (p/p + ) of the base. For a short wavelength corresponding to a high absorption coefficient, the AC photocurrent density is calculated and represented according to the excess minority carrier's recombination velocity at the junction, for different modulation frequency values. The expression of the AC recombination velocity of excess minority carriers at the rear surface of the base of the solar cell is then deduced, depending on both, the absorption coefficient of the silicon material and the thickness of the base. Compared to the intrinsic AC recombination velocity, the optimal thickness is extracted and modeled in a mathematical relationship, as a decreasing function of the modulated frequency of back illumination. Thus under these operating conditions, a maximum short-circuit photocurrent is obtained and a low-cost bifacial solar cell can be achieved by reducing material (Si) to elaborate the base thickness.

Excess minority carrier's diffusion equation in the base of monofaciale silicon solar cell under frequency modulation of monochromatic illumination is resolved. Using conditions at the base limits involving recombination velocities Sf and Sb, respectively at the junction (n + /p) and back surface (p + /p), the AC expression of the excess minority carriers' density δ (T, ω) is determined. The AC density of photocurrent J ph (T, ω) is represented versus recombination velocity at the junction for different values of the temperature. The expression of the AC back surface recombination velocity Sb of minority carriers is deduced depending on the frequency of modulation, temperature, the electronic parameters (D (ω)) and the thickness of the base. Bode and Nyquist diagrams are used to analyze it.

The diffusion coefficient of the minority charge carriers in the base of a silicon solar cell under temperature and subjected to a magnetic field, passes in resonance at temperature (T opt ). For this same magnetic field, the diffusion coefficient of the photogenerated carriers by a monochromatic light in frequency modulation enters into resonance, at the frequency (ω c ). Under this double resonance in temperature and frequency, the diffusion coefficient is used in the expression of the recombination velocity of the minority charge carriers on the back side of the base of the solar cell (n + /p/p + ), to obtain, by a graphical method, the optimum thickness. A modeling of the results obtained shows a material saving (Si), in the development of the solar cell.

The monochromatic absorption coefficient of silicon, inducing the depth of penetration of light into the base of the solar cell, is used through back surface recombination velocity expressions, to determine the optimum thickness necessary for the production of a large photocurrent. The absorption-generation-diffusion and recombination (bulk and surface) phenomena are taken into account in determining the optimum thickness of an n+ -p-p+ bifacial solar cell, for it manufacture process optimization.

The magneto-transport equation relating to the density of photogenerated minority carriers in the (p) base of the (n+/p/p+) solar cell illuminated by monochromatic light in frequency modulation, is solved. The diffusion coefficient of the minority carriers in the base, placed under temperature and magnetic field variation, passes through a maximum, at the double resonance points, in temperature and at the frequency of the cyclotron. The photocurrent is reproduced as a function of the recombination velocity at the junction, for the maximum values of the diffusion coefficient. The expressions of the minority carriers ’recombination velocity on the rear side are deduced and their graphical representation gives the optimum thickness, specific to a high absorption coefficient, for the maximum values of the diffusion coefficient. The results obtained from the optimum thickness are modelled and analyzed, in favor of a reduction of silicon material, for the development of economical solar cells.