Influence of Interconnection Concepts for IBC Solar Cell Performance by Simulation

This work describes interdigitated back-contact cells with a number of different rear side geometries, for different interconnection concepts and module integration, by means of numerical simulations. We show that a simple interconnection concept can be realized with copper wires as bus features and interrupted metal electrodes to avoid shunting, without severe losses compared to multilayer metallization concepts. Using Quokka3, which due to enhanced speed allows for very large simulation sizes, this enables principal investigations undescribed in previous literature. We use this to investigate the disconnection of a single (or multiple) solder joint(s) in terms of device performance, in the case of interrupted metal electrodes. Our findings show that disconnected emitter electrodes cause higher power losses than disconnected BSF electrodes (∼x4), both following a linear relationship. Nevertheless, when multiple of such defects are aligned, the losses are increasing much stronger. We accordingly derive the need to balance design choices such as BSF and emitter width in an industrial implementation, with an empirically derived disconnection probability

Electrode Design for Wire Interconnected Back Contact Solar Cells

Back contact back junction (BC-BJ) solar cells are a well-studied cell concept for high efficiency silicon solar cells. Wire interconnection is a known approach for the interconnection of solar cells with electrodes on front and rear side but has only recently been investigated in combination with back contact concepts [1]. Here, an optimal electrode design has quite different requirements. This study determines the smallest possible electrode geometry for linear electrodes on BC-BJ solar cells by conducting peel tests on geometry variations. Moreover, it is shown that the reliability of the wire interconnection is improved by implementing an optimized H-shaped pad geometry. Consequently, the H-shape is applied on BC-BJ half-cells and evaluated based on peel force measurements, as well as electroluminescence images of wire interconnected half-cells. A significant increase of peel force from below 0.1 N for linear pads to above 0.3 N for H-shaped pads, as well as a significant decrease of failure rate from 12.5 % for linear pads down to 4.5 % are demonstrated

Towards a 300 WP p-Type HIP-MWT-Module - Simulation, Experimental Results and Costs

In this work we are aiming at the goal of fabricating a cost-effective HIP-MWT module exceeding 300W. In order to accomplish this goal HIP-MWT (high-performance metal wrap through) silicon solar cells [1, 2] are fabricated on industrial PERC (passivated emitter and rear cell) precursors. Simulation of the optimal metallization layout for MWT based on measured parameters show cell efficiencies up to 21.5%. The consequentially fabricated HIP-MWT solar cells reach maximum efficiencies of 21.4%. The in parallel processed H-pattern reference cells reach maximum efficiencies of 21.2%. The cell efficiencies show a reduced advantage for MWT than in similar experiments, which is due to the tapered busbars of the reference cells allowing nearly the same short circuit currents. Anyhow, combined with a module interconnection based on back contact foils a cell-to-module (CTM) loss of 2 % is demonstrated which allows module power over 300 WP. Due to a power advantage of about 15W in comparison to H-pattern modules the cost of ownership calculation shows a cost advantage of the HIP-MWT module of 3.2 %. Simulation, experimental results and cost calculation show an advantage for HIP-MWT technology over the H-pattern reference leading to the conclusion that MWT is a more cost-effective concept

Simultaneous Contacting of Boron and Phosphorus Doped Surfaces with a Single Screen Printing Paste

The contact formation by screen printed metal pastes is widely employed in standard solar cell production. To expand the use of screen printed electrodes to n-type solar cells, both boron and phosphorus doped surfaces need to be contacted. To do so with a single material has some advantages especially for IBC solar cells. In this study we test four different screen printing pastes on different boron and phosphorus dopings and in combination with different silicon nitride thicknesses. Phosphorus doping could be contacted over a wide range of sheet resistances, nitride thicknesses and fast firing conditions, leaving much freedom to target the boron contacts. Boron dopings are successfully contacted with all materials, if no capping silicon nitride layer was present. With silicon nitride capping an AgAl and an Ag paste are found to be suitable choices. The lowest contact resistivities with 100 nm SiNX capping determined in this study are C = 0.5 mΩ cm² on phosphorus (Ag) and C = 1.8 mΩ cm² on boron (Ag) doping with one single paste. These results enable highly efficient homojunction IBC cells at low cost

Advancements in the Utilization of Screen-Printed Boron Doping Paste for High Efficiency Back-Contact Back-Junction Silicon Solar Cells

Screen printed boron doping paste can be used as a cost-effective and highly flexible dopant source in silicon photovoltaics. In combination with a co-diffusion approach, it can help mitigate some of the increased costs advanced solar cell concepts inherit. Aiming at the fabrication of high efficiency back-contact back-junction solar cells, we investigate the limitations of direct structured application regarding minimal feature sizes. We find minimal feature sizes of 75 and 120 μm for n ++ - and p ++ -doped regions, respectively. We also demonstrate a fully compatible and homogeneous (ΔR□/R□ = 3% rel ) co-diffusion process, creating all dopings at once