Patterning and metallization of silicon solar cells by inkjet-printed functional ink on a photoresist layer

Abstract

This paper reports a patterning and metallization method for silicon solar cells fabrications. Patterning was achieved by the inkjet printing of a dye-based ink as a mask to protect the photoresist from UV-light initiated crosslinking. The patterned photoresist was used to facilitate the etching of a pattern in the underlying dielectric layer and also to act as a metal plating mask. This method resulted in fine point openings in the photoresist layer with a diameter of 15 Jim and line openings with a width of 30 Jim. Nickel/copper plated homogeneous emitter silicon solar cells with an efficiency of 18.2% on small size Cz wafers were fabricated using this method, may find applications in the metallization of future heterojunction, rear contact and PERC cells.

Metallization Method for Interdigitated Back-Contact Silicon Solar Cells Employing an Insulating Resin Layer and a Ti/Ag/Cu Metal Stack

“…Metal layers comprising 200 nm Ti; 200 nm Ag; a ∼2 nm Ti/200 nm Ag metal stack were sputtered on the rear surfaces of each of 1) IBC precursors with 4-μm-thick spin-coated novolac resin (with resin); 2) IBC cell precursors (without resin); 3) IBC cell precursors with the rear Si nitride (SiN x ) dielectric layers etched by immersion in 1% hydrofluoric acid (Si). The Ti/Ag stacks were sputtered without breaking the vacuum to ensure no contamination occurred at the surface that could impact the adhesion of the Ag to the Ti [15]. The precursors with resin were baked at 160°C for 10 min before metal sputtering to remove residual solvent and ensure that the resin was as stable as possible.…”

“…Additionally, the novolac polymer can be patterned using an inkjet printing process that can result in point openings of diameters ∼20 μm [14], [15]. This can make possible reduced contact fractions and hence reduced contact recombination provided that low contact resistances to both the n + and p + Si regions of diffused IBC cells [16] can be achieved.…”

“…The process flow for fabricating the rear contact structure, which uses the above-described inkjet patterning method, is shown in Fig. 1(b) [14], [15]. Fig.…”

Patterned masking using polymers: insights and developments from silicon photovoltaics

“…In the above-mentioned inkjet-mediated polymer patterning methods, the resolution was limited by droplet spreading on the surface of the polymer due to the need to print sufficient volumes of fluid to either dissolve or plasticise the polymer. In order to reduce the volume of fluid that needed to be printed, Li et al 37,54,153 exploited the chemical amplification technique which was developed to improve the throughput of optical lithography. 5,6 With many chemically amplified resists, optical exposure results in the formation of an acid that, on subsequent heating, catalyses cross-linking.…”

“…Li et al demonstrated the use of this process to create a mask for selective etching 153 and a plating mask for the metallisation on TCO surfaces for heterojunction solar cells. 37 Figure 21 shows a 20 μm wide copper finger on a TCO surface plated through a mask formed using this patterning method.…”