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This paper reports simulations of gradual bandgap CIGS absorber and its impact on the characteristics of a solar cell. The bandgap of the CIGS absorber varies linearly and drops from E gmax (at the junction limit) to E gmin (in the vicinity of the rear contact).We introduce an effective absorption coefficient based on this variation. We will demonstrate that this gradual profile contributes to an improvement up to 171 mV of the open circuit voltage V oc of the cell that is linked to the modification of the internal electrical field distribution within the absorber. However, a joint reduction of 1.50 mA/cm 2 of short circuit current density, J sc , is observed. Overall, the conversion efficiency increases from 19.2%, for a uniform bandgap absorber structure, to 24.9% in that case of gradual bandgap. Additionally, we investigate the impact of absorber thickness and temperature on cell characteristics. [ABSTRACT FROM AUTHOR]

In this work, two process simplifications for n-type PERT (passivated emitter rear totally diffused) bifacial solar cells are investigated. Both are based on a single thermal treatment for elaborating boron and phosphorus doped regions aiming at reducing the number of high temperature steps of standard process. The first simplification shows a mixed co-diffusion from a gaseous source of phosphorus and a boron doped dielectric layer elaborated by low frequency plasma enhanced chemical vapor deposition (PECVD). The second exhibits two independent ion implantations, followed by a co-anneal/activation step. In both cases, implied open-circuit voltages are similar to standard process (~660–670 mV) and emitters allow good contacting by screen-printing ( ρ c =3.0–5.0 mΩ cm 2 ). PERT cells resulting from these processes show very promising performances with efficiency up to 19.7% on industrial 156×156 mm 2 pseudo square Cz wafers. [ABSTRACT FROM AUTHOR]

Although solar cells operate under illumination, most electrical characterization methods are carried out in darkness, which implies some bias. In this work, we study the influence of light on the contact resistivity of the electron and hole contacts of a silicon heterojunction (SHJ) cell using the transfer length method (TLM) method in order to determine them in conditions representative of an operating solar cell at maximum power point. A specific fabrication process has been developed to preserve the passivation level. Therefore, we first focus on the patterning approach used for processing, and show that we can fabricate TLM samples with good passivation properties. Using simulations, we also discuss on the influence of inhomogeneities in the excess minority carrier spatial concentration on the TLM analysis. These inhomogeneities, due to shading, local damages in the passivation or to carrier drift under bias voltage make the measurement complicated to carry out without significant error. Our results suggest that the measurement is more precise in darkness and at very high injection levels, under rear illumination and a low voltage bias. • TLM samples for ρ C (e-) and ρ C (h+) measurement in SHJ cells can be fabricated while maintaining good passivation properties. • TLM measurements are carried out under illumination in order to probe ρ C (e-) and ρ C (h+) under operating conditions. • ρ C is influenced by the excess minority carrier density: it should preferably be extracted under operating conditions. • A meaningful characterization requires a good and homogeneous passivation across the TLM sample, minimal shading and low voltage bias. • Our simulations suggest a moderate impact of light on ρ C (e-) for standard c-Si doping levels. [ABSTRACT FROM AUTHOR]