SECTION INTRODUCTION: Silicon Wafer Photovoltaics

In the consumer-based society in which we live, the expectation is always that we will receive more value in the products we buy every year. As engineers and businesspeople in the solar industry, it’s our job to continue to meet this expectation. Many of us have migrated from the semiconductor industry where we are very familiar with the continued scaling predicted in Moore’s Law. The expectation of continuous improvement is also very active in the solar industry, with the unrelenting drive to grid parity and beyond.

In this issue of Future Photovoltaics, you will find three examples of how innovation is happening and has happened in the crystalline silicon (cSi) space.

Researchers from imec report on a potential solution to reduce the silicon content, thus reducing the highest individual cost component in manufacturing cSi-based solar cells. While achieving efficiencies above 18 percent with an iPERC cell on 130 micron thick wafers, they also address the major challenges with wafers this thin of wafer bowing and carrier recombination.

Chandra Khattak from GT Solar reviews the progress that has been made in the last 35 years in the manufacturing of silicon wafers for solar cells. Since the silicon requirements for solar cells and integrated circuits are different, the evolution has taken very different paths. Dr. Khattak leads us through the progression for the basic Bridgman process to where we are today with high-volume multi-crystalline manufacturing processes based on evolutionary changes from this early starting point.

The third article is a summary of the outcome of the 2nd Workshop on Metallization of Crystalline Silicon Solar Cells. At this conference, almost 200 of the industry’s top engineers in metalization met to discuss future trends. As you will see in this summary, there are still many opportunities, including new pastes, multiple-pass screen-printing, and various plating techniques to optimize the metalization schemes to increase efficiencies. Results of a survey are also included, the general consensus of which is that screen-printing will be the major form of metalization for the next decade.

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