Design of back contact solar cells featuring metallization schemes with multiple emitter contact lines based on TCAD numerical simulations

Abstract

The most hard-working goal within PV community is to design and manufacture devices featuring high-efficiency at low-cost with the better reliability as possible. The key to achieving this target is to optimize and improve the current fabrication processes as well as the layouts of the devices. TCAD modeling of PV devices turns out to be a powerful tool that lowers laboratory manufacturing costs and accelerates optimization processes by bringing guidelines of how to do it. The modeling in TCAD examines the designs before their implementation, accurately predicting its real behavior. When simulations are correctly calibrated, by changing simulations’ parameters, allow finding ways to improve designs’ parameters or just understand better the internal functioning of these devices. In this regard, this Ph.D. thesis fairly treats the electro-optical numerical simulations of interdigitated back-contact (IBC) c-Si solar cells, which nowadays is the architecture to which industry is trying to pull forward because of its numerous advantages. Among the benefits of this design are their improved efficiency due to the absence of front optical shading or the relative simplicity regarding their massive production. The aim of this thesis, it is focusing on providing guidelines of the optimal design parameters of IBC solar cells, based on the state-of-the-art of advanced numerical simulations. Two main topics are treated, (i) the development of a simplified method to compute the optical profiles ten times faster than the traditional one and (ii) an extensive study on the impact of adding multiple striped metal contacts throughout the emitter region improving the efficiency by reducing the inner series resistance. It was performed a large number of ad-hoc calibrated simulations that sweep wide ranges of modeling parameters (i.e., changing geometric sizes, doping profiles, carriers’ lifetimes, and recombination rates) to investigate their influence over the device operation, allowing to identify the most critical ones. This insight leads a better understanding of this kind of solar cells and helps to appraise ways to refine structures and enhance layouts of real devices for either laboratory or industry.