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Magnesium (Mg) anode-electrolyte interaction is not trivial and investigation of the interfacial process can be helpful for the development of Mg batteries. In this work, we studied the Mg metal anode cycled in a chloride (Cl)-free magnesium tetrakis (hexafluoroisopropyloxy) borate electrolyte using a full-cell configuration with TiS$_{2}$ model cathode. Electrochemical measurements and structural analysis of the cathode showed reversible de-/magnesiation of TiS$_{2}$ with some entrapment of irreversibly bound Mg$^{2+}$. Electrochemical impedance spectroscopy (EIS) was applied to analyze the Mg-electrolyte interaction in a three-electrode system. The results showed a rapid increase in charge transfer resistance on the anode side with increasing resting time. In contrast, we observed a significant drop in the charge transfer impedance upon cycling along with the appearance of an additional semi-circle, which suggested to the development of a solid interphase. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) corroborated the EIS results and confirmed the solid interphase layer formation, in which MgF$_{2}$ was identified as the primary species contributing to its formation. The current study provides fundamental insights into the interfacial phenomena between the metallic Mg anode and Cl-free electrolyte by highlighting the role played by the formed interphase on the reversible Mg stripping and plating in a Mg full-cell.

33rd European Photovoltaic Solar Energy Conference and Exhibition; 649-656, Since its first publication in 2015, the PERC+ cell concept has been rapidly adopted by several solar cell manufacturers worldwide. The fast industrial implementation is facilitated by the very similar process technology of bifacial PERC+ cells and main stream monofacial PERC cells. Conversion efficiencies of industrial PERC+ solar cells up to 21.6% with front side illumination and 17.3% with rear side illumination were reported. Meanwhile, four companies are offering commercial bifacial PERC+ modules with maximum rating power around 300 Wp when illuminated from the front side, only. These modules apply 60 PERC+ cells with 4 or 5 busbars, which are interconnected by conventional stringing and tabbing technology. First small scale outdoor installations verify an increase of the energy yield relative to monofacial PERC modules between 13% and 22%. Two large scale out door installations with 2 MWp and 20 MWp are under construction in Taiwan and China, respectively. We report for the first time in detail on a novel bifacial PERC+ prototype module by applying the Smart Wire Connection Technology. We interconnect 18 halved PERC+ solar cells by soldering 18 wires directly to the Ag front and Al rear fingers. The resulting prototype module exhibits independently confirmed front and rear side efficiencies of 19.8% and 16.4%, respectively. Additionally, Meyer Burger certified a full-size PERC+ SWCT module according to the IEC 61215 norm thereby demonstrating the long term reliability of this novel module technology.

31st European Photovoltaic Solar Energy Conference and Exhibition; 264-272, We demonstrate a procedure for quantifying efficiency gains that treats resistive, recombinative, and optical losses on an equal footing. For this we apply our Conductive Boundary (CoBo) model as implemented in the Quokka cell simulator. The generation profile is calculated with a novel analytical light trapping model. This model parametrizes the measured reflection spectra and is capable of turning the experimental case gradually into an ideal Lambertian scheme. Simulated and measured short circuit current densities agree for our 21.2%-efficient screen-printed PERC cell and for our 23.4%-efficient ion-implanted laser-processed IBC cell. For the loss analysis of these two cells we set all experimentally accessible control parameters (e.g. saturation current densities, sheet resistances, and carrier lifetimes) one at a time to ideal values. The efficiency gap to the ultimate limit of 29% is thereby fully explained in terms of individual improvements and in terms of their respective synergistic effects. This approach allows comparing loss structures of different types of solar cells, e.g. PERC and IBC cells.

31st European Photovoltaic Solar Energy Conference and Exhibition; 341-350, Passivated Emitter and Rear Cell (PERC) solar cells are currently being introduced into mass production. In this paper we report a novel PERC solar cell design which applies a screen-printed rear Al finger grid instead of the conventional full-area aluminum (Al) rear layer while using the same PERC manufacturing sequence. We name this novel cell concept PERC+ since it offers several advantages. In particular, the Al paste consumption of the PERC+ cells is drastically reduced to 0.15 g instead of 1.6 g for the conventional PERC cells. The Al fingers create 2 μm deeper Al-BSFs which increases the open circuit voltage by 3 mV. The 5 busbar Al finger grid enables bifacial applications of the PERC+ cells with front side efficiencies up to 21.2% and rear side efficiencies up to 16.7% measured with a black chuck. The corresponding bifaciality is up to 80.0%. When measured with a reflective brass chuck, the PERC+ cells demonstrate efficiencies up to 21.5% compared to conventional PERC cells with 21.1% efficiency. Whereas ISFH developed the aforementioned PERC+ results, SolarWorld independently pioneered a very similar bifacial PERC+ cell process starting in 2014. Transfer into mass production has been successfully accomplished and novel glass-glass bifacial PERC+ modules have been launched at the Intersolar 2015 based on a most simple, lean and cost-effective bifacial cell process. These new bifacial PERC+ modules show an increase in annual energy yield between 5 and 25% in simulations which is confirmed by first outdoor measurements.

27th European Photovoltaic Solar Energy Conference and Exhibition; 557-560, Screen-Printed PERC solar cells are a promising candidate for next-generation industrial-type solar cells. Industrial PERC cell process flows typically involve wet chemical polishing of the rear side in order to reduce the surface roughness and to improve the conversion efficiency. In this paper, we show that Al2O3/SiNx passivation stacks achieve an excellent surface recombination velocity below 10 cm/s even for small polishing removal of 5 μm corresponding to rough surfaces. In contrast, SiOx/SiNy passivation stacks exhibit a strong increase of the surface recombination velocity up to 30 cm/s for rough surfaces. Accordingly, we find that the efficiency of PERC solar cells with Al2O3/SiNx rear passivation is almost independent of the polishing etch depth with best efficiencies up to 19.7% for 7.5 μm polishing removal whereas the efficiency of SiOx/SiNy rear passivated PERC cells strongly decreases for rougher surfaces.

27th European Photovoltaic Solar Energy Conference and Exhibition; 672-675, Passivated emitter and rear cells (PERC) are considered to be the next generation of industrial-type screen-printed silicon solar cells. However, today there exist only few deposition methods for rear passivation layers which meet both, the high-throughput and low-cost requirements of the PV industry in combination with high-quality surface passivation properties. In this paper, we evaluate and optimize a novel deposition technique for AlOx passivation layers applying an inductively coupled plasma (ICP) plasma-enhanced chemical vapour deposition (PECVD) process. The ICP AlOx deposition process enables high deposition rates of up to 5 nm/s as well as excellent surface recombination velocities below 10 cm/s after firing. When applied to PERC solar cells the ICP AlOx layer is capped with a PECVD SiNy layer. We achieve independently confirmed conversion efficiencies of up to 20.1% for large-area (15.6x15.6 cm2) PERC solar cells processed at ISFH with screen-printed metal contacts and ICP AlOx/SiNy rear side passivation on standard boron-doped Czochralski-grown silicon wafers. The internal quantum efficiency reveals an effective rear surface recombination velocity Srear of (90 ± 30) cm/s and an internal rear reflectance Rb of (91 ± 1)% which demonstrates the excellent rear surface passivation of the ICP AlOx/SiNy layer stack. PERC solar cells processed in the Q-Cells Research Line achieve efficiencies up to 19.6% with ICP AlOx/SiNy rear passivation which is comparable to the reference process at Q-Cells.