Modeling and Investigation of Rear-Passivated Ultrathin CIGS Solar Cell

Abstract

In this paper, we use numerical simulations to investigate ultrathin Cu (In1−xGax) Se2 solar cells. In the first part, we focus on the cell configuration in which the PV parameters fit and match the fabricated cell characteristics. Our goal is to investigate the impact of different loss mechanisms, such as interface trap density (Dit) and absorber trap density (Nt), in different cell pitch sizes on cell performances. Dit defines the number of carrier traps at CIGS/Al2O3 interfaces to recombine with photogenerated carriers. Nt defines the number of carrier traps in the absorber layer. Recombination through traps has been found to be the primary loss process in the investigated cell. Additional numerical simulations reveal appreciable gains in cell performance for various cell pitch sizes, absorber doping densities, Ga content, and graded bandgap under AM1.5 illumination. Research during the recent decade has clarified that the most promising strategy to achieve maximum efficiency consists of the so-called tandem configuration. Therefore, we here propose a u-CIGS/PERT silicon device employing, as a top cell, a u-CIGS cell optimized to take into account the above procedure. The results of these simulations provide insights into the optimization of ultrathin-film CIGS solar cells.