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A novel diffusion system for in-line rapid thermal diffusion is presented. The lamp-heated furnace has a low thermal mass and a metal free transport system based on the walking beam principle. The furnace has been used to process first solar cells with lightly and highly doped emitters respectively. Solar cells with shallow lightly doped emitters show that the emitters processed in the new device can be well passivated. Shallow emitters with sheet resistances of up to 40 /sq. have been contacted successfully by means of screen printing and firing through a SiNx antireflection coating. [Copyright &y& Elsevier]

In this paper we give a mathematical derivation of how luminescence images of silicon solar cells can be calibrated to local junction voltage. We compare two different models to extract spatially resolved physical cell parameters from voltage images. The first model is the terminal connected diode model, where each pixel is regarded as a diode with a certain dark saturation current, which is connected via a series resistance with the terminal. This model is frequently used to evaluate measurement data of several measurement techniques with respect to local series resistance. The second model is the interconnected diode model, where the diode on one pixel is connected with the neighbor diodes via a sheet resistance. For each model parameter at least one image is required for a coupled determination of the parameters. We elaborate how also the voltage calibration can be added as an unknown parameter into the models, and how the resulting system of equations can be solved analytically. Finally the application of the models and the different ways of voltage calibration are compared experimentally. [ABSTRACT FROM AUTHOR]

Laser microstructuring of thin dielectric layers on sensitive electronic devices, such as crystalline silicon solar cells, requires a careful design of the laser ablation process. For instance, degradation of the substrate's crystallinity can vastly decrease minority carrier lifetime and consequently impair the efficiency of such devices. Short-pulse laser ablation seems well suited for clean and spatially confined structuring because of the small heat-affected zone in the remaining substrate material [Dube and Gonsiorawski in Conference record of the twenty first IEEE photovoltaic specialists conference, 624-628 ]. The short-time regimes, however, generate steep temperature gradients that can lead to amorphization of the remaining silicon surface. By 'heating' the substrate via a non-ablative laser pulse in the nanosecond regime before the actual ablation pulse occurs we are able to prevent amorphization of the surface of the silicon solar cell substrate, while lowering the ablation thresholds of a SiN layer on crystalline silicon wafers. [ABSTRACT FROM AUTHOR]

Abstract: High-efficiency silicon solar cells with evaporated front contacts and an oxide-passivated rear require post metallization annealing (PMA). In an industrial environment the evaporated front contacts are replaced by screen printed contacts for fast processing and cost reasons. The PMA conditions necessary for optimum rear side passivation can be inferior to such a front side metallization. In order to design a PMA supporting contact in future, this paper investigates what mechanism deteriorates the contact resistance of screen printed front side metallization during nitrogen PMA. Scanning electron microscopy (SEM) on samples with increased contact resistance reveals an altered microstructure at the silver–silicon contact interface that is proposed to impede current flow and hence increases the contact resistance. We present a model that describes the mechanism of contact deterioration during nitrogen PMA. [Copyright &y& Elsevier]