Optimization of the thickness of the doping rate base (Nb) of the (n+/p/p+) silicon solar cell with vertical multi-junctions connected in series and placed under monochromatic illumination in frequency modulation

Abstract

The silicon solar cell with vertical multi-junctions (MJV) connected in series, is studied under monochromatic illumination in frequency modulation, for different cases of doping rate of its base. The diffusion equation relating to the density of minority charge carriers in the base of the solar cell is solved, taking into account the dynamic coefficient of diffusion (D(ω,N_b)) related to the doping rate (Nb) and to the frequency (ω) of modulation, as well as recombination speeds (Sf) at the junction and (Sb) on the rear face. From the expression of the photocurrent density of the minority charge carriers, the expressions (S_b (H,D (ω,N_b))) of the dynamic rate of recombination of the minority charge carriers on the rear face of the base, are established . Their graphical representations as a function of the thickness (H) of the base, makes it possible to determine the optimum thickness (Hopt), for different doping rates, for different frequency zones. The optimum Optimization … Malick NDIAYE et al.

AC Back Surface Recombination Velocity as Applied to Optimize the Base Thickness under Temperature of an (n<sup>+</sup>-p-p<sup>+</sup>) Bifacial Silicon Solar Cell, Back Illuminated by a Light with Long Wavelength

“…In this interval of low frequencies, the relaxation time of the minority carriers is important (large values of D in Equation ( 5)), allowing a large distance of travel (Einstein relation). A large optimum thickness of the base is then obtained [43] [57] [58] (Figure 9). On the other hand, at high frequency values, the relaxation time (ωτ  1) of minority carriers is reduced, as well as the coefficient (Equation ( 5)) and the scattering length (Equation ( 9)) of minorities corresponding to a short travel distance, then the optimum thickness [57] [58] of the base needed to collect the charge carriers is small, regardless of the temperature.…”

Derivative of Ac back surface recombination velocity as applied to n+/p/p+ silicon solar cell optimum base thickness determination: Effect of both temperature and frequency

“…Previous works have plotted dynamic diffusion coefficient [14,15,[38][39][40][41][42] of minority carriers in the base of the solar cell (Eq. 7).…”

“…In figure 6 the optimum thickness of the base increases versus the diffusion coefficient D(ω, T) whatever the zones of modulation frequency [17,18,42] , as expressed in (Eq. 7).…”

AC back surface recombination, as applied to determine (p) base thickness of both conventional and vertical series junction (n+/p/p+) silicon solar cells under white illumination

“…[36][37][38][39] of graphical determination of the optimum base thickness (Hopt) of solar cells. Solar cells are, either horizontally illuminated by (n+), or vertically illuminated over all the different regions of the solar cell [40,41] . Expressions of (Sb1V), (Sb2 recombination velocity (Sb2H) gives the optimum thickness (Hopt) for the conventional solar cell.…”

“…The use of light frequency modulation [37][38][39][40] makes it possible to influence minority charge carriers' recombination parameters in the bulk (diffusion length L(ω) and diffusion coefficient D(ω) ) and on the back surface. Then several cases of solar cells are observed according to the conditions of regimes, static (ωτ <<1) and dynamic (ωτ >>1).…”