- Increasing the amount of sunlight confined in the silicon absorber material through reduced reflectance loss and loss due to optical absorption in the coating;
- Eliminating the color variations of the solar cells and saving on costs associated with the manual color binning process;
- Enhancing the passivation properties of the deposited coating, which increases the cell efficiency;
- Depositing back-surface passivation film which allows to reduce the wafer thickness and save significantly on material cost
Figure 4 illustrates the achieved results so far for replacing the traditional SiNx AR coating in the typical multi-crystalline silicon solar cell manufacturing line. The blue curve shows the traditional optical performance of today’s routine SiNx AR coating. The residual reflectance in the blue region explains the bluish and mosaic appearance of most of the multi-Si solar cells. The normalized number of photons through the SiNx coating is 95.4% at best.
AccuStrata deposits a graded index coating (the red curve of Figure 4), which increases the amount of photons reaching the silicon absorber to 98.2%, or by 2.8%, improving the average efficiency of the cells by 0.45% absolute. AccuStrata’s coating is comprised of a complex layer with a gradient refractive-index profile.
AccuStrata has already implemented the optical monitoring and adaptive correction parts of its platform technology on OTB Solar’s (Netherlands) multi-crystalline silicon solar manufacturing lines in India and USA. AccuStrata is currently in the process of delivering a gradient-index antireflective and hydrogenating (passivating) thin film coating, where will provide remarkable expertise, know-how and IP.
Currently this technology is also deployed in a manufacturing facility in Tempe, AZ and can be showcased to potential customers.
Our company’s technology increases crystalline silicon cell efficiency, and hence increases the generated power by each individual solar cell by 3-5% (3% already demonstrated). As solar cell manufacturers sell their products on a $/Watt basis, the increase in average solar cell efficiency immediately increases their profit margins, as they are able to sell more power at the same cost.
Additionally, AccuStrata’s broadband coating darkens the cells, i.e. eliminates the color variations from cell to cell and the need for manual color binning, saving additional cost to manufacturers. Moreover, by developing a technology for back surface passivation, AccuStrata enables reduction of wafer thickness from the current 180 mm down to below 130 mm, or more than 25%, reducing expenditures for raw material by ~20%.Thin Film Solar Technology: AccuStrata’s solution for reducing the cost of thin film solar panel is also focused on increasing the power solar panels generate by controlling:
- Film thickness and film uniformity over the solar panel
- Short- and long-term drifts of film thickness and uniformity
- Film optical properties, their variation over substrate area and homogeneity in film depth
- Film density, its uniformity and drifts
- Film porosity, water content and related degradation
- Film material band-gap, uniformity, homogeneity, time drift
- Film spectral scattering coefficient and its distribution over the solar panels
AccuStrata’s control system operates by monitoring spectral reflectance and scattering as the solar panels move through the deposition chambers. The control system takes immediate corrective actions as soon as deviations are detected by performing minor, real-time re-optimization of the remaining part of the process sequence in order to compensate for the detected error and adjusts the subsequent deposition processes to achieve a near “gold standard design”.
AccuStrata’s dynamic control systems increase thin film solar panel efficiency, and hence increase the generated power by 10-15%.
The company’s product for thin film solar panels was first deployed in 2010 at Sencera International in Charlotte, NC. In 2014 AccuStrata signed a large commercial contract with a CIGS thin film manufacturing company in Albany, NY. Currently it is also under advanced negotiations for deployment of the technology to customer facilities in USA and Japan.