- By Dr. Chris Eberspacher, Chief Technology Office, Applied Materials, Solar Business GroupApplied Materials -
For the first time, the solar industry has achieved a critical mass, combining strong financial resources, top global scientific and engineering talent and highly capable, cost-effective manufacturing tools and processes. This critical mass is following the same path that created the huge expansion of the semiconductor industry in the 1980s, and it has already begun to significantly shift the economics of photovoltaic technology.
We spoke with Chris Eberspacher, Chief Technology Officer of Applied’s Solar Business Group, about the innovations in solar manufacturing technology that we can expect to see in the near future.
1. How will manufacturing technology help to achieve greater than 20% efficiency for crystalline silicon modules?
- The key is to manufacture higher efficiency cells without the higher costs that accompany more complex fabrication schemes. This requires innovative materials and processing technologies. For example, we’ve developed advanced passivation films that provide surface recombination velocities (SRV) of less than 25cm/sec. Using a proprietary method to enhance silicon oxide growth rate, we have produced SRV values comparable to
those obtained using slow, low growth-rate oxidation tube systems, but with many times higher throughput. This work demonstrates a pathway for c-Si PV manufacturers to considerably enhance average c-Si cell efficiencies in high-volume mass production.
2. Is there a roadmap to increase efficiency inthin film modules?
- We are devoting significant technological resources to improving the key deposition processes used for higher-efficiency tandem junction devices that combine amorphous (a-Si) and microcrystalline (μc-Si) materials. For example, continuous development of our PECVD 5.7 system has steadily enhanced the system’s ability to tune the physical characteristics of the microcrystalline and other layers for increased efficiency. Our ATON™ PVD 5.7 system is being continuously improved in the same way. These programs give materials scientists and process developers superior production tools so they can quickly go from lab to fab.
3. The material properties of TCO play a big role in efficiency. Can we expect further improvements in this key process for higher cell efficiency?
- We have deposited repeatable, uniform, high-conductance, optimally-textured ZnO coatings on 1.4m2 substrates in our labs. Very early in the process development, we measured photocurrent densities comparable
to the world’s best laboratory coatings. Our customers will soon be able to take full advantage of these developments in their production lines.
4. Do large-area substrates pose a uniformity challenge for micro-crystalline silicon deposition?
- The large surface area of the substrates - 5.7m2 - challenges plasma-based deposition process uniformity because it is hard to control the precise plasma conditions. We are currently demonstrating better than +/- 4 rel% crystalline fraction uniformity in production and better than +/- 4 rel% conversion efficiency uniformity on the full 5.7m2 size. This uniformity greatly reduces the variability of the end product and reduces “binning” to almost negligible levels, resulting in enhanced profitability.
5. What is Applied Materials doing to decrease Light Induced Degradation (LID) in thin film devices?
- Using single-junction as an example, we havedeveloped processes that reduce the LID effect from up to 25 rel% of initial power to about 15 rel%. This gains back 10 rel% of the power that would have otherwise not been available. Similar gains are possible with tandem junction structures.
6. The question on everyone’s mind is grid parity. Will this happen anytime soon?
- Our goal of parity with mainstream energygeneration is in sight in many markets. As a direct result of the gains made in manufacturing technology, I believe that the near future holds vast potential for PV to not only meet, but exceed, the cost-efficiency of conventional power sources.