Voltage increase for thin silicon solar cells utilizing epitaxial lateral overgrowth

Abstract

Epitaxial lateral overgrowth (ELO) has been used to achieve a reduced p-n junction area for thin Si solar cells with the goal of achieving increased voltage. The n-Si absorber is grown by ELO on the p+ Si substrate. In this work, a novel ELO mask is designed, in which the effects of different factors on the voltage can be analyzed separately. The mask design starts from a basic ELO solar cell structure, where there is only one p-n junction. With this structure, the factors that can be studied include the light generation area to p-n junction area ratio, orientation of the growth layer, geometry of the p-n junction and the dielectric material. The second structure has two p-n junctions, with coalescent Si layer resulting from the ELO. The voltage of the selective planar cells has been analyzed first in this work. It shows that the lateral overgrowth region may have a poor quality that results in a loss in open circuit voltage (Voc) and fill factor (FF). The analysis in this work will be the guidance for the future ELO reduced junction thin Si solar cells.