On the impact of substrate contact resistance in bifacial MIS-type lifetime structures
2022, Herguth, Axel, Kostrzewa, Fabian, Sperber, David
Bifacial metal-insulator-semiconductor (MIS) structures are used to intentionally manipulate field-effect passivation of dielectric layers on crystalline silicon substrates during lifetime measurements by external biasing. It is found that the impact of biasing on surface passivation depends on the quality of the substrate contact, in particular in asymmetric front/rear biasing conditions. A mathematical model is presented and used to demonstrate the problems arising from a high substrate contact resistance.
On improved passivation stability on highly-doped crystalline silicon and the long-term stability of regenerated Cz-Si
2018-10, Sperber, David, Herguth, Axel, Hahn, Giso
Different surface passivation approaches are applied on Cz-Si and FZ-Si samples and long-term stability is investigated during treatments at 60–80 °C and up to 1 sun equivalent illumination intensity. It is shown that SiNx:H and AlOx:H/SiNx:H surface passivation show a much more stable passivation quality when deposited on P-diffused and B-diffused surfaces, respectively. Long-term measurements lead to the conclusion that Cz-Si samples fired at measured peak temperatures up to 750 °C are very stable after regeneration of bulk defects. Samples fired at 850 °C show much stronger bulk-related degradation potentially linked to light and elevated temperature induced degradation (LeTID). Furthermore, Cz-Si samples fired at 850 °C express an instable behavior after a regeneration treatment.
A Detailed Study on Light-Induced Degradation of Cz-Si PERC-Type Solar Cells : Evidence of Rear Surface-Related Degradation
2018-09, Herguth, Axel, Derricks, Christian, Sperber, David
A light-induced degradation phenomenon of unknown origin in p-type Cz-Si passivated emitter and rear cell (PERC)-type solar cells is thoroughly investigated by collating results from different measurement techniques and predictions from various simulations. The observed degradation manifests in slight losses in jsc, strong losses in Voc, and devastating losses in FF, and thus massively impacts efficiency. It is found that the series resistance degrades significantly due to a degradation of front contact resistance. This, however, does not explain losses in Voc and jsc, which are attributed to the degradation of a different cell component. Neither a degradation by defect formation in the space charge region, nor the emitter, nor the bulk is found to consistently explain the observations. Only a rear surface-related degradation mechanism explains consistently all experimental findings.