Ines Dani

In-Line Plasma-Chemical Etching of Crystalline Silicon Solar Wafers at Atmospheric Pressure

Atmospheric pressure plasma technologies are a potential substitution for wet chemical and vacuum processes in the production of crystalline silicon solar cells, leading to a simplified in-line processing chain. In this contribution, a plasma chemical etching technology is presented as a basic step for a future continuous production process. A linearly extended DC arc discharge is used for activation of the etching gases. An Ar-N2 mixture is fed through the plasma source; etch gases are injected into the afterglow plasma, near the substrate. Controlled purge gas systems prevent the contamination of the reaction zone with air or moisture as well as the release of reaction products. The plasma source was studied by a noninvasive in-line monitoring of the DC arc phenomena. Silicon etching rates can be controlled by the etch gas composition and the plasma conditions. Fourier Transform infrared spectroscopy of the waste gas was applied to monitor the current etching rates. First industrial tests confirmed standard efficiencies of the cells after edge isolation by atmospheric pressure plasma etching.

Investigation of the Thermoelectric Power Factor of KOH-Treated PEDOT:PSS Dispersions for Printing Applications

Abstract This work studies the modification of commercially available dispersions of intrinsically conductive polymer PEDOT:PSS with a strong base, KOH. It is concluded that addition of base derives a dedoping of the PEDOT chain and increase Seebeck coefficient from 15 µV/K to 90 µV/K. Supportive UV-Vis-NIR spectroscopy was used for tracking the doping level of the polymer. A surface morphology study of the dedoped PEDOT:PSS films was monitored by SEM. It was shown that if KOH is used in excess with respect to the acid component of PEDOT:PSS dispersions, it segregates at the surface forming crystallites. They, however could be easily removed by methanol rinsing without destroying the sample integrity. After material modification, a dispenser-printed polymer unileg-TEG with 61 unicouples was fabricated by printing. The TEG in form of 253 mm-long stripe shows a flexible behavior. At 90 K temperature difference a resulting power output of ~ 100 nW could be measured. We suggest that the low power output is due to a high internal generator resistance.

Energy Turnaround: Printing of Thermoelectric Generators

Waste heat in the temperature range up to 100 °C can be found in virtually all areas of industry and building and is often the hardest to recover cost-efficiently. It accounts for more than 50 % of the total heat generated in industry [1].

In-Line Plasma Etching at Atmospheric Pressue for Edge isolation in Crystalline Si Solar Cells

In this contribution dry etching of crystalline silicon solar cells in a novel atmospheric pressure plasma is described. Dry etching has the potential to replace wet chemical etching steps in solar cell processing. Unlike in other dry etching systems described recently a plasma arc operating at atmospheric pressure is employed, offering the advantage of reduced investment costs and better process integration. Removal of the emitter from the rear surface is expected to lead to a reduction in surface recombination velocity and can be particularly useful for future cell concepts with dielectric rear surface passivation. Good shunt resistance values were achieved and the cell efficiencies are comparable to results from the reference process