A new cost-effective and efficient approach is proposed for texturing the crystalline silicon using the gas lift effect (GLE). The advantages of this approach over the conventional ones are that significantly lower amounts of IPA is used and much shorter etching time is required to achieve the same reflectivity. GLE is generated by taking advantage of the hydrogen bubbles evolved between the silicon wafer being etched and a glass plate, placed in parallel, creating a gap of 1-2 mm. This effect then acts as a pumping mechanism detaching more bubbles from the silicon surface, accelerating them to the top and out of the system, as quickly as they are generated. Experiments were carried out with various combinations of TMAH/IPA concentrations for two different GLE conditions to analyze and determine their influence on etching time, etching rate, surface morphology and reflectivity of the textured silicon surface. The use of this new approach in surface texturing, allowed the reduction of the required IPA by 50% and etching time by more than 60% to achieve the same reflectivity. This can ultimately lead to a significant reduction in cost by increasing the efficiency of the texturing process. A combination of 3.5% IPA and 2 mm GLE resulted in a textured silicon surface having a low specular Solar Weighted Reflectivity (SWR) of 0.15%.

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Modeling and simulation techniques were used to understand the fluid flow patterns inside the silicon texturing system operating under gas-lift effect (GLE) for solar cell applications. Experiments were performed which confirmed the validity of the simulation model and the simulated results. It was determined that due to the original non-optimal inlet, the fluid flow pattern and the non-uniform fluid velocity distribution inside the system resulted in the generation of lower velocity regions on the surface of the textured silicon. The simulation tool validated the correlation of the lower fluid velocity with the reduced surface coverage, uniformity and subsequent less optimal surface reflectivity. Various inlet designs were modeled and evaluated for optimal performance. The best case inlet design was fabricated and tested resulting in the validation of the simulation work and significant improvement in the GLE texturing system performance. With the new inlet design, as the fluid velocity reaches and goes beyond some critical value (in this case 0.047 m/s) in areas that had shown lower velocity in the original inlet design (mainly close to the inlet and side walls), the observed morphology and surface reflectivity improve significantly with values very similar to those of the higher-velocity areas.

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Texturing the surface of the silicon-based solar cells significantly increases the light absorption contributing to their overall efficiency. Wet anisotropic etching technique utilizing the novel gas-lift effect (GLE) approach is an effective and low-cost approach for texturing commercial silicon solar cells. Two solar cell devices, one based on the novel GLE texturing approach and the other based on the conventional method, were designed, fabricated, and characterized. A significant improvement (more than 100%) was observed in the efficiency of the solar cell based on the GLE texturing approach. This improvement may be contributed to the significant impact of utilizing the GLE approach on increasing the real surface area (resulting in higher electron-hole pair generation) and increased light absorption (decreased reflectivity). The application of the new GLE texturing approach results in considerable improvements in overall power efficiency of silicon solar cells without any additional increase to the production cost. V C 2013 AIP Publishing LLC. [http://dx.