Significant Enhancement in Surface Passivation Property of Micro–Textured Silicon Surface with Thin Hydrogenated Intrinsic Amorphous Layer    

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ABSTRACT

In the present study, one step low-cost alkaline potassium hydroxide (aqueous solution) method was implemented on Czochralski silicon and Float zone silicon wafers for micro-texturing under identical parameters that improve light harvesting property of the wafers. At the rear interface of micro-textured Czochralski and Float zone silicon, a few nm thin layer of hydrogenated intrinsic amorphous silicon and n-type nano crystalline silicon was deposited, which not only addressed the parasitic loses at rear interfaces but also provides excellent passivation via back surface field to the micro-textured silicon surfaces. The minority carrier life time measurement was done on symmetric structure (i-a-Si:H/µT-n-Si/i-a-Si:H). The minority carrier lifetime is found 2.31 µs and 677.79 µs for the unpassivated and hydrogenated intrinsic amorphous silicon passivated micro-textured silicon Czochralski surfaces. Similarly, the measured lifetime of the micro-textured Float zone for unpassivated and passivated silicon surfaces are found 2.77 µs and 1788.30 µs. The high implied open circuit voltage of the micro-textured silicon wafers after deposition of hydrogenated intrinsic amorphous silicon (for passivated Czochralski and Float zone silicon are 708 mV and 714 mV respectively) indicates improvement in the collection property of electrons at the cathodic interface. The reflectance data, measured on symmetric structure, before and after hydrogenated intrinsic amorphous silicon layer deposition confirms that the incorporation of passivation layer does not affect light harvesting property of the micro-textured silicon wafers. Thus, stack of hydrogenated intrinsic amorphous/n-nano-crystalline silicon thin layers could be an effective interface passivation layer for futuristic high-performance hetero-junction solar cells (HJSCs) i.e., HIT, hybrid solar cells under optimize parameters for full potential.

Significance of the Study:

This study demonstrates a low-cost, one-step alkaline KOH method for enhancing the light harvesting properties of micro-textured silicon surfaces, applicable to Czochralski (CZ) and Float Zone (FZ) silicon wafers. The incorporation of hydrogenated intrinsic amorphous silicon (i-a-Si:H) and nano-crystalline silicon (n-nc-Si:H) layers significantly improves surface passivation and reduces parasitic losses. The findings provide critical insights into optimizing passivation strategies for achieving higher efficiency in next-generation heterojunction solar cells.

Summary of the Study:

The study explores the impact of micro-texturing and surface passivation on CZ and FZ silicon wafers using a KOH process and thin i-a-Si:H/n-nc-Si:H layers. Enhanced minority carrier lifetime (MCLT) of 677.79 µs (CZ) and 1788.30 µs (FZ) and implied open-circuit voltages of 708 mV (CZ) and 714 mV (FZ) validate the effectiveness of the passivation layers. Reflectance data confirm no compromise on light harvesting properties. The findings establish the potential of these passivation strategies for high-performance heterojunction solar cells.