-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer review by the scientific conference committee of SiliconPV 2016 under responsibility of PSE ScienceDirect Impact of Ag pads on the series resistance of PERC solar cells

Abstract Screen-printed passivated emitter and rear cells (PERC) require Ag pads on the rear side to enable solderable connections for module integration. These Ag pads are separated from the silicon by a dielectric layer to avoid recombination of minority charge carriers. The drawback of this configuration is an elongated transport path for the majority charge carriers generated above the pads. This results in an increase in series resistance. The strength of this effect depends on charge carrier generation above the Ag pads that critically depends on shading of the cell's front side. Ag pads are usually wider than the busbars or the interconnector ribbons and thus are only partially shaded. We build PERC test structures with various rear side configurations of Ag and Al screen printing as well as with and without laser contact openings (LCO). Using experiments and finite element simulations we investigate the impact of shading the Ag pads by the busbars and other means. While fully shaded regions do not increase the lumped solar cell's series resistance, unshaded Ag pads lead to an increase of about 37%

In-Line High-Rate Deposition of Aluminum Onto RISE Solar Cells by Electron Beam Technology

This paper presents results on the contact formation to Rear Interdigitated Single Evaporation Emitter Wrap Through (RISE EWT) solar cells by electron beam high-rate evaporation of aluminum. In stationary depositions water cooled copper crucible and ceramic crucibles were used. The ceramic crucibles were found to be best suitable when regarding the electron beam power and the upper limit of the solar cell temperature of 400 °C. Using an in-line high-rate deposition equipment 20 ?m-thick aluminum layers were deposited at dynamic deposition rates of 3.6 ?m×m/min from ceramic crucibles onto RISE EWT solar cells. The cell temperature during deposition was measured and analyzed using 2-dimensional finite-element (FEM) simulations. The processed RISE EWT solar cells present efficiencies of up to 18.4 %, which equals the cell efficiencies of reference solar cells that are contacted at lower deposition rates at lab scale