CIGS Mini‐Modules with Dispensed Metallization on Transparent Conductive Oxide Layer

Abstract

This article presents the application of a parallel dispensing device for low‐temperature silver paste metallization on transparent conductive oxide (TCO) layers of Cu(In1 − xGax)Se2 (CIGS) substrates as an alternative metallization technology to screen printing and inkjet printing. A curing variation experiment is performed to analyze the effect of different curing conditions on the resulting contact resistivity of the metal grid. Contact resistivity values below 5 mΩcm2 are achieved. Furthermore, CIGS mini‐modules are metallized with three different low‐temperature paste formulations obtaining a record core finger geometry of 25 μm and an average optical aspect ratio of 0.46 using 25 μm nozzle openings. The dispensed metal grid on the TCO layers achieves the comparable current density values of jsc = 32.2 mA cm−2 and the open‐circuit voltages values per cell of Voc = 672 mV as the screen printed metal grid on CIGS mini‐modules and, hence, a nominal power of 2.05 W. The metal grid enables the use of broader cell widths compared with grid‐free CIGS samples and results in a reduced dead area.

Increasing the Effective Area of Small‐Sized CIGS Modules by Printed Ag Front Contacts

“…In previous studies, microscope images illustrate this difference. [ 19,28 ] It is expected that the electrode pitch differences of Δ = 0.012 mm do not cause this difference in module performances for both metallization technologies. The front contact metallization enables CIGS module designs with wide cells, especially dispensed Ag‐electrodes.…”

“…The choice of these parameters is based on the findings in our previous experiments. [ 19 ] Subsequently, the metalized CIGS substrates are characterized regarding the achieved Ag‐electrode shapes (3D‐microscopy) and the electrical performances (TLM measurements, I–V measurements). The electrode width can be described by the shading electrode width w shading and the core electrode width w core .…”

“…Further information about the stacking sequence Mo/CIGS/chemical bath deposition (CBD)‐CdS/i‐ZnO/ZnO:Al/ITO is presented in our previous study. [ 19 ] The P1P2P3 interconnection width is w P1P2P3 = 300 μm for all small‐sized CIGS modules used in this study. It should be mentioned that industrial fabricated CIGS modules can show narrower scribing lines down to w P1P2P3 = 150 μm.…”

“…The optical aspect ratio AR o is calculated by the ratio of the maximum electrode height h f,max to the shading line width w shading . [23] The advantageous application of the dispensing process on CIGS substrates is depicted in Figure 1 and has been presented in the study by Gensowski et al [19] . Further, both scanning electron microscope (SEM) images in Figure 1 show a homogeneous Ag-electrode shape on CIGS substrates but paste-specific geometric dimensions result from different paste properties.…”

“…[ 12,13 ] The question arises of which metallization techniques are suitable for CIGS modules, especially in the case of upscaling module sizes. On the R&D level, metal grids on CIGS substrates are realized by flatbed screen printing, [ 14–16 ] inkjet printing, [ 17,18 ] parallel dispensing, [ 19 ] and plating. [ 20 ] In addition, the metal grid design requires adaptations to realize optimal use of silver in terms of module power.…”