Development of in-situ doped poly-SiOx passivating contacts for high-efficiency solar cells
P. Guo (TU Delft - Electrical Engineering, Mathematics and Computer Science)
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Abstract
Carrier-selective passivating contacts (CSPCs) is now a popular contact structure that effectively passivates the crystalline silicon (c-Si) surface as well as selectively extracts the specific type of charge carrier (electrons or holes). In this thesis work, we developed the CSPCs based on oxygen-alloyed polycrystalline silicon (poly-SiOx) passivating contacts, which shows less parasitic absorption compared with the polycrystalline silicon (poly-Si) passivating contacts.
In order to deploy poly-SiOx CSPCs in c-Si solar cells, we optimized the oxygen content, doping level, high-temperature annealing as well as the hydrogen passivation process. As a result, the excellent passivation for n-type poly-SiOx passivating contact on both flat surface (implied-VOC of 727 mV and J0 of 2.4 fA/cm2) and textured surface (implied-VOC of 723 mV and j0 of 6.9 fA/cm2) and for p-type poly-SiOx passivating contact on flat surface (implied-VOC of 709 mV and J0 of 13.9 fA/cm2) are obtained.
With the optimized poly-SiOx passivating contacts, the front and back contacted (FBC) solar cells were fabricated in this thesis. An excellent fill factor of 83.5% was obtained in the solar cell with front and rear poly-SiOx passivating contacts, indicating an efficient carrier transport and collection. An active area efficiency of 21.5% featuring Jsc of 40.8 mA/cm2 was measured on a front side textured FBC solar cell with the optimized poly-SiOx passivating contacts. It indicates the potential for achieving a conversion efficiency of above 23.0 % with the same cell configuration in the short term.