In this work, we propose a method to determinate the optimum thickness of a monofacial silicon solar cell under irradiation. The expressions of back surface recombination velocity depending the damage coefficient (kl) and irradiation energy (p φ) are established. From their plots, base optimum thickness is deduced from the intercept points of the curves. The short-circuit currents Jsc0 and Jsc1 corresponding to the recombination velocity Sb0 and Sb1 are determinated and a correlation between the irradiation energy, the damage coefficient and optimum thickness of the base is established.

The monochromatic absorption coefficient of silicon, inducing the light penetration depth into the base of the solar cell, is used 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 the excess minority carrier continuity equation. The solution of this equation gives the photocurrent according to absorption and electronic parameters. Then from the obtained short circuit photocurrent expression, excess minority carrier back surface recombination velocity is determined, function of the monochromatic absorption coefficient at a given wavelength. This latter plotted versus base thickness yields the optimum thickness of an n + -p-p + solar cell, for each wavelength, which is in the range close to the energy band gap of the silicon material. This study provides a tool for improvement solar cell manufacture processes, through the mathematical relationship obtained from the thickness limit according to the absorption coefficient that allows base width optimization.

The minority carrier's recombination velocity at the junction and at the back surface is used for the modeling and determination of the optimum thickness of the base of a silicon solar cell in the static regime, under magnetic field and temperature influence. This study takes into account the Umklapp process and the Lorentz effect on the minority carriers photogenerated in the base.

Excess minority carrier's diffusion equation in the base of monofaciale silicon solar cell under frequency modulation of polychromatic 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 expression of the excess minority carriers' density  is determined. The density of photocurrent Jph (T, ) is represented according to the recombination velocity at the junction for different temperature values. The expression of the ac back surface recombination velocity Sb of minority carriers is then deduced depending on frequency of modulation, temperature, electronic parameters (D) and the thickness of the base. Bode and Nyquist diagrams are used to analyze, both diffusion coefficient and back surface recombination of excess minority carriers submitted to Umklap process.

Geometric parameters are an important data for the choice of solar cell architecture, for better conversion performance. As poor optoelectronic material is used, i.e. short minority carrier's diffusion length and under concentrated light which increases the temperature, it is then important to optimize the width of the lamella in order to have better photogenerated charge collection. Thus the intent of this work is the determination of the width of the lamella structure, presented through phenomelogical parametersmodeling study. These are the diffusion length and coefficient, as well as the surfacerecombination velocity of the photogenerated carriers in the base of the lamella silicon. The result gives a mathematical relationship between the optimum width and the operating temperature of the lamella solar cell, allowing to influence the industrial manufacturing process for the material economy.