Technological innovations in increasing solar cell efficiency – Part 1

Technological innovations in increasing solar cell efficiency – Part 1

In this 2-part series we shall briefly look at the innovations that improved the solar cell efficiency over the years.

Starting from the 1990’s we see how each innovation improved efficiency incrementally. As we saw earlier, using the data from NREL’s Cell Efficiencies chart, we found that the efficiency had improved by 0.7% point every year. In this hard fought battle to absorb more and more photons in lesser and lesser area, many innovations have played a key role.

We shall look at a few of them today:

1. Back Surface Field (BSF) - Boosting Electron Collection (1990’s): In 1990, Siemens AG introduced an ingenious technology known as Back Surface Field (BSF) to enhance the efficiency of solar cells. Imagine a solar cell as a light-trapping net, catching energy from the sun. The back surface of the cell is often prone to letting some of this energy slip away due to electrons recombining prematurely. Siemens' solution was to add a layer of aluminum to the back of the solar cell. This aluminum layer acted as a protective shield, stopping those electrons from recombining before they could be gathered to generate electricity. This improved the overall efficiency of the solar cell by about 2%, a seemingly small change that made a notable impact.

2. Buried Contact Solar Cells - Shining Light on Efficiency (1990’s): In 1992, BP Solar introduced the Buried Contact Solar Cells. Imagine a solar cell as a light-sensitive puzzle; each piece needs sunlight to work together. More the sunlight, better it works. However, earlier cells had a problem – metal contacts on the front shaded the cell, blocking sunlight leading to 10% to 15% shading losses. BP Solar's solution was to carve tiny grooves into the solar cell's surface, like sunlit valleys. These grooves, or trenches, were then filled with metal contacts, reducing shading and letting sunlight flood the cell. This improved in efficiency by reducing shading losses to only 2% to 3%. By "burying" the contacts within these grooves, BP Solar unlocked more surface are to work with the sunlight, increasing energy output. This advancement allowed solar cells to capture light more effectively, converting it into electricity.

3. Screen-Printed Contacts - Painting Efficiency (1990s): In 1994, Sharp Corporation introduced a groundbreaking method called Screen-Printed Contacts, revolutionizing how solar cells were crafted. Imagine solar cells as canvas, waiting for an artist's touch. Previously, a complex photolithography process was used to add metal contacts, like delicate brushstrokes. Sharp changed the technique by using screen printing, a more efficient and cost-effective technique. It's like painting on the canvas with precision. This innovation meant that the metal contacts were applied in a simpler, faster, and less expensive way, improving the solar cell's efficiency by about 1%.

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