A low cost additive-free acid texturing process for large area commercial diamond-wire-sawn multicrystalline silicon solar cells

• Published in: Solar energy Vol. 205; pp. 263 - 274
• Main Authors: Sreejith, K.P., Sharma, Ashok K., Behera, Siddharth, Kottantharayil, Anil, Basu, Prabir K.
• Format: Journal Article
• Language: English
• Published: New York Elsevier Ltd 15-07-2020; Pergamon Press Inc
• Subjects: Acids; Additive-based acid texturing; Circuits; Cost analysis; Current density; Diamond machining; Diamond wire sawn multi-crystalline wafers; Emitters; Energy efficiency; High efficiency industrial multi-crystalline silicon cells; Industrial production; Kerf; Low cost; NCPRE additive-free acid texturing; Open circuit voltage; Optimization; Photovoltaic cells; Sawing; Short circuit currents; Short-circuit current; Silicon; Slicing; Solar cells; Solar energy; Texturing; Wafers; War; Wire; Additive-based acid texturing; NCPRE additive-free acid texturing; Diamond wire sawn multi-crystalline wafers; High efficiency industrial multi-crystalline silicon cells
• ISSN: 0038-092X; 1471-1257
• DOI: 10.1016/j.solener.2020.05.018

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•An additive-free acid texturing process is demonstrated for the DWS multi-crystalline silicon wafers in solar cell manufacturing industry.•These textured wafers have similar optoelectronic and electrical properties as that of industrial additive-based acid textured DWS wafers.•The reported additive-free textured cells have similar batch average efficiency to that of the additive-based acid textured cells in industrial production.•Further optimization of fabrication conditions, our proposed textured wafers will possibly increase the cell efficiency.•Proposed texturing scheme cut-down nearly 60% of chemical cost of additive-based acid texturing process presently used in industry.
Diamond-wire-sawing (DWS) technique allows slicing of silicon ingots to produce wafers at cheaper price due to its reduced kerf-loss and increased cutting rate. However, there is no cost-effective and industrially viable method available for texturing DWS wafers, especially for multicrystalline silicon (mc-Si) wafers. Currently additive-based acid texturing process is availed by PV manufacturing units for texturing DWS mc-Si wafers. An additive-free, low cost and energy-efficient acid texturing process is demonstrated for DWS mc-Si wafers in industrial production line. Nearly 10% absolute reduction in weighted average reflectance values (WAR) are noticed for the newly textured wafers from that of as-cut DWS mc-Si wafers and the WAR values are comparable to that of existing additive-based acid textured mc-Si wafers. An absolute reduction in emitter saturation current density by ~17 fA-cm-2 and improved implied open circuit voltage of ~5 mV (absolute) are reported for lifetime sample fabricated using newly textured wafers when compared to the additive-based acid textured lifetime samples. An impressive batch average efficiencies of 18.20% and 18.24% are achieved for the additive-free and existing additive-based acid textured mc-Si cells, respectively. Detailed analysis conclude that ~1.5% (relative) enhancement in short circuit current density can be achieved by further process optimization. Cost analysis indicates that 60% of the chemical cost involved the texturing process can be cut down by replacing the existing additive-based acid process with the new method using the same process equipment. Hence, the texturing process presented has great potential for producing large area high efficiency mc-Si cells favoring cost considerations without compromising performance.