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

• Main Authors: Cheolmin Park, Gyeongbae Shim, Nagarajan Balaji, Jinjoo Park, Junsin Yi
• Format: Article
• Language: English
• Published: MDPI AG 2020-06-01
• Series: Energies
• Subjects: boron tribromide (BBr3); bonding coordination complex; boron-diffused layer; n-type c-Si solar cell
• Online Access: https://www.mdpi.com/1996-1073/13/12/3057

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 (R_sheet). The correlation between boron–silicon bonding in coordination complexes and electrical properties according to the R_sheet 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 (τ_eff), implied open-circuit voltage (iV_oc) 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 iV_oc exceeded 660 mV. Additional gains of 670 and 680 mV were obtained for the passivation layer AlO_x/SiN_x stack and SiO₂/SiN_x 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%.