AC COMPOSITE BACK SURFACE RECOMBINATION VELOCITY AS APPLIED TO N+/P/P+ SILICON SOLAR CELL OPTIMUM THICKNESS BASE DETERMINATION

A composite light in frequency modulation is used for on an n+/p/p+ crystalline silicon solar cell. The density of the photogenerated minority carriers in the base (p) of the solar cell maintained in short circuit is obtained by resolution of the continuity equation, taking into account the condition at the back surface limit, characterized by (Sb) the recombination velocity. Expressions of this ac recombination velocity are obtained through the study of the ac photocurrent, depending on the recombination velocity at the junction (Sf). One of the expressions takes into account the spectral composition of the illumination, while the second materializes the intrinsic recombination velocity associated to diffusion. The graphic analysis of the expressions of the ac recombination velocity (Sb) according to the thickness (H) of the base, leads to the determination of the optimum thickness (Hopt) of the base allowing the extraction of the maximum photocurrent. This optimum thickness (Hopt) is modelled on the modulation frequency () and the effective diffusion coefficient (D ()). A decrease in (Hopt) with frequency shows the possibility of reducing the thickness of the base of the solar cell during its industrial development process.