The influence of an annealing step at about 500°C after emitter diffusion of multicrystalline solar cells is investigated. Neighboring wafers from a silicon ingot were processed using different annealing durations and temperatures. The efficiency of the cells was measured and detailed light beam induced current measurements were performed. These show that mainly areas with high contents of precipitates near the crucible walls are affected by the anneal. An efficiency increase from 14.5 to 15.4% by a 2h anneal at 500°C was observed. The effect seems to be more likely external than internal gettering

Minority carrier recombination is studied in multicrystalline ingot cast silicon solar cells. The normalized recombination strength Gamma of dislocations is obtained by correlating topograms of the internal quantum efficiency (IQE) with those of the dislocation density rho. Gamma is obtained by fitting an extended theory of Donolato to the experimental data. The measured Gamma-values vary significantly between adjacent dislocation clusters and correlate with the spatial pattern of the dislocations. All Gamma-values are strongly dependent on the parameters of the solar cell process. The influence of phosphorus diffusion and hydrogenation is shown. After solidification of the silicon, impurities from the crucible enter the ingot and deteriorate its border regions during cooling to room temperature. These deteriorated border regions can be significantly improved by an additional low temperature anneal that is applied after phosphorus diffusion. The experiments indicate that the mechanism of the anneal is external phosphorus gettering into the emitter

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In this work it is studied the influence of different texturizations on minority carrier lifetime of n-type Fz silicon wafers passivated with thin amorphous silicon layers (a-Si:H). For amorphous-crystalline silicon based heterojunction solar cells a good light trapping is essential. Therefore a front side texturization is needed as it can increase the photocurrent due to its low reflectance. The interface between the amorphous emitter and the crystalline base plays an important role for two reasons: firstly, the micromorphic surface topology can generate different deposition regimes that results in different lifetimes, and secondly, the nanomorphic structure also show influences on the lifetime. We compare two different types of wet chemical texturizations by different carbonate solutions and a plasma texturization subsequently covered by a thin layer of a-Si:H by means of plasma-enhanced chemical vapor deposition. The surface morphology produced by the texturization on the silicon wafers is analyzed by scanning electron microscopy and atomic force microscopy. The quality of the passivation of the textured silicon surface by the a-Si:H deposition is evaluated by measuring minority carrier lifetimes with a microwave photo-conductance decay and quasi steady state photo-conductance devices