A 3D model for thickness and diffusion capacitance of emitter-base junction in a bifacial polycrystalline solar cell

Through this paper, we present n+-p-p+ solar cell. Mathematical relations describing the generated carriers’ density are expressed, using among others a new approach involving both junction and back surface recombination velocities in a 3D modelling study.Based on the normalized carriers’ density versus the base depth and operating an open circuit voltage, we study the space-charge layer thickness (Z) versus various parameters such as the grain size (g) and the grain boundaries recombination velocity (Sgb). Hence, the relationship between Z and the diffusion capacitance show that junction in the n+-p-p+ solar cell, when the columnar orientation is considered, is characterized by the plane capacitor properties

Influence of grain size and grain boundary recombination velocity on the diffusion capacitance of a polycrystalline bifacial silicon solar cell

Une etude a trois dimensions qui tient compte de la taille des grains et des joints de grain est utilisee pour determiner la densite des porteurs minoritaires de charges en exces dans la base dfune cellule solaire au silicium polycristallin. Le concept de vitesse de recombinaison a la jonction SFu est utilise pour traduire la maniere dont les porteurs minoritaires photogeneres traversent a la jonction. Ainsi, une nouvelle approche de la capacite de diffusion de la cellule est definie pour les trois modes dfeclairement de la photopile solaire (eclairement avant, eclairement arriere et le double eclairement). Les courbes de la capacite de diffusion ont permis dfetudier lfinfluence des parametres suivants : la taille de grain (g), la vitesse de recombinaison aux joints de grains (Sgb), la vitesse de recombinaison a la jonction SF, la longueur dfonde ƒÉ et le mode dfeclairement (u). Lfetude de la capacite montre que les vitesses de recombinaison a la jonction SFu et aux joints de grain Sgb jouent un role primordial surtout pour les petites tailles de grain. A 3D modelling study is used to determine the excess minority carrier density expression in the base of a polycrystalline bifacial silicon solar cell. The concept of the junction recombination velocity SFu is used to quantify how carriers flow through the junction: based on this concept, a new approach of the solar cell diffusion capacitance is presented for three illumination modes (front side, back side and both front and back sides). The plot of the diffusion capacitance allowed us to study the influence of the following parameters: grain size, grain boundary recombination velocity, junction recombination velocity and illumination wavelength on this capacitance. This study pointed out that junction and grain boundary recombination velocities play an important role especially for small grain size