Correlation between Boron–Silicon Bonding Coordination, Oxygen Complexes and Electrical Properties for n-Type c-Si Solar Cell Applications

Abstract

In this paper, the relationship between coordination complexes and electrical properties according to the bonding structure of boron and silicon was analyzed to optimize the p–n junction quality for high-efficiency n-type crystalline solar cells. The p+ emitter layer was formed using boron tribromide (BBr3). The etch-back process was carried out with HF-HNO3-CH3COOH solution to vary the sheet resistance (Rsheet). The correlation between boron–silicon bonding in coordination complexes and electrical properties according to the Rsheet was analyzed. Changes in the boron coordination complex and boron–oxygen (B–O) bonding in the p+ diffused layer were measured through X-ray photoelectron spectroscopy (XPS). The correlation between electrical properties, such as minority carrier lifetime (τeff), implied open-circuit voltage (iVoc) and saturation current density (J0), according to the change in element bonding, was analyzed. For the interstitial defect, the boron ratio was over 1.8 and the iVoc exceeded 660 mV. Additional gains of 670 and 680 mV were obtained for the passivation layer AlOx/SiNx stack and SiO2/SiNx stack, respectively. The blue response of the optimized p+ was analyzed through spectral response measurements. The optimized solar cell parameters were incorporated into the TCAD tool, and the loss analysis was studied by varying the key parameters to improve the conversion efficiency over 23%.