3D-printed battery stack based on a zinc-based battery cell technology with aqueous electrolytes (AZIB) during curing in a UV curing chamber. AZIBs offer a high potential in terms of cost reduction of active materials and manufacturing processes, a high availability of raw materials using non-critical raw materials as well as increased intrinsic safety and environmental compatibility due to the water-based electrolyte. More details can be found in article number 2300723, Oliver Fitz and co-workers.
To evaluate the impact of industrially relevant contact firing parameters on the contact resistance of screen printed front side silver contacts to the n-type emitter of crystalline silicon solar cells, contact firing is performed using design of experiments. Therefore, H-pattern aluminum back surface field solar cells processed on boron-doped Czochralski silicon are contact fired by rapid thermal firing in an industrial conveyor belt furnace as well as in a single wafer reactor. Current-voltage data as well as contact resistance values of 36 parameter sets are analyzed and evaluated regarding the significance of several contact firing parameters. Further aspects of the current transport mechanisms and performance of front side silver contacts in correlation with their microstructure are revealed. Comprehensive macroscopical characterization as well as microstructural analysis is done. An efficiency gain of ≥ 0.1%abs only due to optimization of contact firing parameters is shown.
We investigate two chemical random texturing methods on mono crystalline silicon wafers. To simulate an industrial process 25 p-type monocrystalline silicon (10/spl times/10) cm/sup 2/ wafers are textured in one step. We compare aqueous solutions consisting of potassium hydroxide (KOH) and isopropyl alcohol (IPA) and solutions consisting of sodium carbonate (Na/sub 2/CO/sub 3/) and sodium hydrogen carbonate (NaHCO/sub 3/). The dependence of the reflectance on etching time, solution temperature and concentration is shown. We achieved weighted reflectance values as low as 12.5% and 16.5% respectively with the two solutions. Furthermore homogeneity and pyramid size are reported. Industrial type solar cells with a homogeneous emitter and screen printed contacts were processed. Efficiencies up to 16.6% with textured surfaces could be achieved for screen printed solar cells on 1 /spl Omega/cm p-type Cz silicon wafers.
Cell concepts that feature via-holes, like the emitter wrap-through concept, suffer from higher series resistance losses than conventional solar cells. A part of these resistance losses is due to the fact that a small size element, in this case a via-hole, has to collect the current of a wide area on the front side, which leads to the so-called spreading resistance. An analytical equation already exists which describes the spreading resistance effects that are present in these cells. This equation is an accurate description for a quadratic or hexagonal pattern of via-holes. For cells that feature an interdigitated metallization grid on the rear side, like emitter wrap-through solar cells, the arrangement is often nonsquare because the distance between two via-holes is different in the x- and y-directions. In this paper, it is shown that the existing formula is in excellent correlation with the results from simulation program with integrated circuit emphasis (SPICE) simulation if a quadratic symmetry element is chosen. The SPICE simulation is then adjusted for nonsquare symmetry elements, showing that the existing formula is not valid for these arrangements and has to be modified. The derived analytical modification is adapted to yield a better description of the spreading resistance in the emitter of such a cell structure for variable via-hole distances in the x- and y-directions. The relative deviation between the simulation results and the analytic approach is less than 15%. This enables an accurate calculation of the resistance losses of relevant technological configurations.
In this paper we report about first results regarding laser fired contacts (LFC) on an optimized screen printed aluminum rear side layer and compare it with our standard LFC procedure on evaporated aluminum layers. First of all, the influence of the laser pulse energy, pulse duration and amount of pulses on the resistance of one contact is evaluated. Since this value depends strongly on the size of the contact also the recombination losses in the contact area have to be considered in order to compare and qualify LFC contacts comprehensively. We have achieved cell efficiencies > 18.0 % on industrial like processed wafers, which underlines the potential of this approach. Finally, a 20.5 % efficiency solar cell with an aerosol printed front metallization manufactured on laboratory scale is presented, which is the best value ever reported for solar cells with fired front and back side metallization.
This paper presents a transient reduced-order model of squirrel cage induction machines for multiphysics simulation environments. By solving a differential-algebraic system of equations parametrized by magnetostatic finite element calculations, the model enables both fast and accurate results for system simulations. Therefore, the model is applicable to the electro-mechanical analysis of electrified drivetrains in the whole operation range. Properties and simplifications of this model are discussed. The impact of the simplification of sinusoidally distributed rotor currents is reported with a numerical example.
Abstract In this work, lithium‐ion battery full‐cells based on spruce‐derived hard carbon anodes and an electrochemical pre‐lithiation method are presented in combination with a detailed analysis of full‐cell operation and the lithiation state. The physical and electrochemical properties agree well with those of previous biomass‐derived hard carbon anodes. However, low initial coulombic efficiencies of 65 % represent one of the major challenges of the developed anodes with respect to full‐cell operation. To counteract the initial lithium loss, in‐situ electrochemical pre‐lithiation was conducted, allowing battery operation in the same cell setup without reassembly. Consequently, significantly increased capacities, cycle life, and first cycle coulombic efficiency were obtained in comparison to untreated anodes (195 mAh/g versus 150 mAh/g, state of health (SOH) 80 after 150 cycles versus 70 cycles, and 90 % versus 65 %). In summary, spruce‐based hard carbon has the potential to be an environmentally friendly alternative to standard graphite.
The cost-effective production of highly efficient solar cells and modules is one of the major goals of current research activities. Especially the ongoing crisis that is affecting a major part of the solar industry makes new methods and instruments for further reductions in cost of ownership (€/Wp) of solar cells and modules essential. Our approach is the optimization of the metallization layout of passivated Czochralski-Si metal wrap through (MWT) solar cells aiming at minimum module cost of ownership. The front finger width, the number of contact rows and the number of solder pads per contact row are varied methodically using analytical modeling. The results of the simulation provide the basis for a bottom-up cost of ownership calculation of MWT solar cells and modules. MWTmetallization layouts with more than four contact rows are identified as most cost-effective. A comparison between MWT and conventional H-pattern technology reveals a cost advantage of over 2 % relative for the MWT approach on module level.
