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This work evaluates the potential of selective epitaxy to mitigate the recombination losses at the p-type contact regions of plated bifacial n-type PERT cells. Following the growth of a 500 nm, 2.5 10(19) cm(-3) boron doped epitaxial layer at the emitter contact regions defined by laser ablation of the passivating dielectrics, both an increase in V-oc (+6 mV) and FF (+ 1% absolute) are measured in the final cells compared to the reference with a homogeneous diffused emitter. These results come with an average efficiency gain of 0.3 and 0.5% absolute for front and rear side illumination, respectively. If the diffused, blanket emitter in the passivated regions is replaced by a thicker, lowly doped epitaxial profile (3 mu m, 5 10(18) cm(-3)) to further reduce recombination, an additional rise in implied V-oc after metallization of 10 mV is estimated. This increase would be the result of a reduction in J(0,pass, emitter) (down to 6 fA/cm(2)) and J(0,plated, emitter) (down to 1967 fA/cm(2)).

Deep diffusion of phosphorus atoms in monocrystalline silicon using laser doping process has been studied in this work. A pulse modulated CW fiber laser of wavelength 1070 nm with microsecond pulses has been used to diffuse phosphorus from pre-deposited spin-on-dopant film. The surface and cross-sectional morphology has been studied using SEM and AFM. The concentration-depth profiling was done using PP-TOFMS. Deep junctions of more than 10 µm have been obtained under various laser doping conditions while a maximum junction depth of 51.3 µm has been obtained through optimization. Diffusion depth enhancement is made possible by increasing the pulse length and reducing laser scan speed. Laser doping led to formation of n + region with surface concentration varying in the range of 3×10 20 –5×10 20 cm −3 for varying scan speed. Cross-sectional TEM and diffraction studies on laser irradiated samples show presence of only monocrystalline silicon phase after laser induced melting and solidification.

In this study, the contact formation of aluminum containing silver metallization pastes for boron emitters was investigated. Model pastes with varied glass composition (PbO-containing and PbO-free) and Al content were prepared. It was found, that glass viscosity as well as Al content have a strong influence on densification behavior of the pastes. The most significant effect of the aluminum addition is the change of the thermodynamic conditions in the system silver-glass-silicon. For investigations of the contact formation an in-situ-contact resistance measurement was performed. The interface morphology of the pastes in dependence on the firing temperature was investigated by means of cross section samples in SEM and EDX. Finally, n-type Si solar cells were electrically characterized and the IV-data were correlated to the interface morphology. (C) 2015 The Authors. Published by Elsevier Ltd.