Electrical properties of fine line printed and light‐induced plated contacts on silicon solar cells

Abstract

The properties of fine-line printed contacts on silicon solar cells, in combination with light-induced plating (LIP), arc presented. The seed layers are printed using an aerosol system and a new metallization ink called SISC developed at Fraunhofer ISE. The influence of multiple layer printing on the contact geometry is studied as well as the influence of the contact height on the line resistivity and on the contact resistance. The dependence between contact resistance and contact height is measured using the transfer length model (TLM). Further on, it is explained by taking SEM images of the metal semiconductor interface, that a contact height of less than 1 mu m or a minimum ink amount of only 4-6 mg is sufficient to contact a large area (15.6 cm x 15.6 cm) silicon solar cell on the front side and results in a contact resistance R-c x W < 0.5 Omega cm. As the line resistivity of fine-line printed fingers needs to be reduced by LIP, three different plating solutions are tested on solar cells. The observed differences in line resistivity between rho(f) = 5 x 10(-8) and 2 x 10(-8) Omega m are explained by taking SEM pictures of the grown LIP-silver. Finally, the optimum LIP height for different line resistivities is calculated and experimentally confirmed by processing solar cells with an increasing amount of LIP silver

Study of electron tunneling mechanism by co-firing process for high efficiency crystalline Si solar cells

“…The silver metal, glass layer formed by glass frit in the paste during co-firing process at Si surface, and a-SiNx:H film were removed by using 3 HNO and HF mixture solutions to delineate the footprints of the etched Ag crystallites into the Si surface [5].…”

Study of the high throughput flexographic process for silicon solar cell metallisation

“…Previous work has shown that lines with a metallised area well below 100% can provide good solar cell properties after Ag‐LIP . For that reason, the most important response to take into account for the process optimisation is the line width followed by the line metallised area.…”

Synthesis of a Lead- and Particle-free Metal-organic Ink for Front Side Metallization of Crystalline Silicon Solar Cells

“…Rising silver prices affect the production costs because of the silver required for metallization: Solely the front side metallization accounts for about 20 % of standard cell production costs [1]. However, the front-side metallization is also vulnerable to many losses, including resistivity at the metal/semiconductor interface, line resistivity of fingers, and losses due to optical shading [2].…”

“…The composition of the ink components with regard to etching depth, contact formation and resulting silver layer is essential for the second metallization step by light-induced plating [2,5]. Curing temperature and duration have been varied to obtain best results [6].…”

“…Left: Comparing DSC curves of SiNx powder with bismuth-neo solution (solid green[1]), zinc-neo solution (dotted purple[2]), Ag-neo powder (dotted blue[3]), and our26 wt% metal content ink (solid red[4]). Right: EDX image of an etched pyramid by a low-concentration ink cured at 500 °C for 5 min.…”