The development of the advanced semiconductor finger solar cell

Abstract

The advanced semiconductor finger solar cell is a silicon wafer cell designed for industrial implementation. The concept incorporates a selective emitter with a front side grid metallisation that combines the advantages of both screen printing and plating techniques. Screen‐printed metal forms the busbars and a few thick but widely spaced fingers. The current is carried to these fingers via narrow, closely spaced, thinly plated, laser‐doped lines formed perpendicular to the fingers. This paper explains the evolution from the original semiconductor finger cell design to this advanced version and outlines the issues encountered in the process development thus far. An encouraging result of 18.5% efficiency has been achieved on a large area cell with fully industrial equipment, and several opportunities for significant improvement are identified. Copyright © 2013 John Wiley & Sons, Ltd.

Review of Laser Doping and its Applications in Silicon Solar Cells

“…This meant fingers could be placed further apart with a multitude of resulting benefits including less optical shading, self-aligned screen-print metallization, and reduced metal/Si interface (as the metal fingers only contacted the silicon where they intersected the SFs). Originally the SFs were formed in a similar manner to the buried contact solar cell (laser grooving followed by thermal diffusion), later, laser doping was implemented to form the SFs whereby an SOD was applied, and laser doping was performed through the SiN x dielectric layer [57], [58], making the technology more commercially viable and also compatible with lower quality wafer types. In the advanced laser-doped semiconductor finger solar cell concept, the SFs were plated with a thin layer of metal after the screen-printed fingers were formed, improving contact resistance at the intersecting points and improving the lateral conductivity of the SFs meaning the screen-printed fingers could be placed further apart again.…”

Reducing shadowing losses with femtosecond‐laser‐written deflective optical elements in the bulk of EVA encapsulation

“…For instance, laser‐grooved buried contact cells show less optical shadowing and a lower series resistance than screen‐printed c‐Si cells. Furthermore, the front side grid of c‐Si solar cells can be made by deposition of a narrow (10–30 µm) seed contact line, which is thickened in a subsequent galvanic plating process . The aspect ratio of these fingers is higher than that of conventionally screen‐printed ones, leading to higher efficiencies .…”