OPTIMIZATION OF PHOSPHORUS EMITTER USING POCl3 DIFFUSION FOR PERC CELLS

Date

2023-5-11

Author

Keçeci, Ahmet Emin

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The active dopant profile and the enhanced passivation of the emitter are keys to improving passivated emitter and rear contact (PERC) solar cell efficiency. PERC cells evolved from the standard Al-BSF cells that suffered from recombination losses due to full-area metal contact at the rear side. PERC cell technology enables to reduce the metal contact fraction and considering the total saturation current density (J0), the emitter region has the biggest share. In this work, the optimization of the profile and the passivation of the emitter are investigated. Emitters are formed by using a liquid source phosphoryl chloride (POCl3) diffusion process. By varying drive-in conditions, desired profiles can be formed for phosphorus diffused regions. Enhancement in the passivation is observed on the symmetrical emitter samples by using thermally grown silicon dioxide due to its low interface defect density (Dit). In addition, we show that a low temperature annealing process (LTA) at 700°C for 60 minutes after the silicon nitride (SiNx) deposition improves the surface and the bulk passivation especially for emitters with high surface concentrations (≈3E20 cm-3). According to the results of the symmetrical emitter samples, the saturation current density of the emitter (J0,e) is reduced from 100 to 60 fA/cm2 by varying the profile without changing the sheet resistance and below 40 fA/cm2 by increasing the sheet resistance.

Subject Keywords

Emitter, Passivation, Liquid source diffusion

URI

https://hdl.handle.net/11511/103516

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Graduate School of Natural and Applied Sciences, Thesis