OPTIMIZATION OF EMITTER LAYER IN N-TYPE BIFACIAL CRYSTALLINE SOLAR CELL

2022-5-09
Salimi, Yasaman
P-type solar cells currently hold most of the market share in industrial solar cell fabrication statistics. NREL's highest efficiency record for p-type crystalline perc cells is 22.8%. However, there is an ever-increasing interest in n-type wafers due to the many advantages they have against p-type cells. According to the ITRPV's estimation, the n-type cell structures will be taking half the industry's share by 2031. Compared to p-type cells, n-type cells yield better efficiency and lifetime values and are not affected by boron-oxygen defect and light-induced degradation (LID). However, the processes of boron emitter doping and passivation in this cell type can be challenging. Also, a boron-rich layer (BRL) forms during the boron doping process. Due to the high density of inactive boron atoms, BRL acts as a high carrier recombination site. As a result, it is essential to effectively remove and replace it with another layer that effectively passivates the emitter surface. Therefore, the primary work of this thesis is to optimize the boron doping recipe resulting in uniformly doped emitter regions. Various thermal and chemical oxidation recipes were tested and optimized. Different passivation stack layers were also tested in order to achieve the best imp Voc results. The firing temperatures were optimized, aiming to achieve good contact resistivity values while preserving the imp Voc. Finally, the bifacial solar cell was produced utilizing the optimized values as a proof of concept. The fabricated cells have been characterized and analyzed with an efficiency of 18.2% and a Voc of 0.631 V.

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Citation Formats
Y. Salimi, “OPTIMIZATION OF EMITTER LAYER IN N-TYPE BIFACIAL CRYSTALLINE SOLAR CELL,” M.S. - Master of Science, Middle East Technical University, 2022.