Different Wafer Sizes For Different Applications

‘Unity in diversity’ aptly describes the evolving landscape of wafer formats in the PV industry. Unlike in the past, when wafers were predominantly full or pseudo-square, PV manufacturers are now increasingly adopting rectangular wafer formats.

This shift allows companies to explore various dimensions that are deemed optimal, while still conforming to certain module dimension standards agreed by the industry, all thanks to the versatility offered by rectangular wafer formats. Trina Solar was one of the early adopters of one such rectangular wafer format – 210 x 182 mm, commonly referred to as 210R – while also continuing the usage of G12 (210 x 210 mm) as well. The company was also an early adopter of TOPCon cell technology. 

Lukas Chao Ye, product manager of Trina Solar, shared the company’s experience in adopting the i-TOPCon (industrial TOPCon) brand name for the company’s TOPCon technology, to rectangular wafer formats and the corresponding product development roadmap at the TaiyangNews High-Efficiency Solar Technologies 2023 Conference (see Lukas Chao Ye, Trina: Adapting TOPCon to Rectangular Wafer Formats).

Global landscape of wafer formats 

Quoting a market study report by Trina Solar, Chao Ye shared insights into the global cell capacity and estimated production figures, focusing on wafer dimensions for 2023 and 2024. The study highlighted that the major rectangular cell dimensions are 210R, 191 x 182 mm (191R), and 199 x 182 mm (199R). By the end of 2023, the global production capacity for rectangular cells was to hit 84 GW, with 14.5 GW of it reflected in actual production. Looking ahead, the capacity is projected to surge to 420 GW in 2024, accounting for over 80% of the cell market share. The production of rectangular cells is expected to range between 200 GW and 300 GW this year. 

These findings were corroborated by InfoLink Consulting’s Photovoltaic Technology Trends Report from September 2023, which noted the complete replacement of M6 or 166 mm and smaller wafers with 210 mm and 182 mm technologies. Furthermore, the report indicates that more than 80% of the cell capacity now utilizes 210R TOPCon technology. It emphasizes that the 210 mm wafer size is poised to become the mainstream choice for PERC, TOPCon, and HJT technologies in the foreseeable future. 

Evolution of i-TOPCon cell technology 

Since starting with a production capacity of 500 MW and using wafer sizes of 158 x 158 mm in 2015, Trina Solar has significantly advanced its i-TOPCon technology, achieving a mass efficiency of 23.5%. By 2019, through continuous R&D, the company attained a maximum TOPCon cell efficiency of 24.58%, as certified by ISHF. Chao Ye highlighted that Trina Solar has implemented TOPCon technology with the larger 210 mm wafer size over the past 2 years. Within this brief period, the company’s initial 500 MW pilot line reached a mass-production efficiency of 24.5%, while the maximum cell efficiency at the lab scale hit 25.15%. This enhanced series was named i-TOPCon Plus, incorporating the G12 wafer size and SMBB technology to boost optical performance.

In 2023, i-TOPCon advanced technology was further refined to include both G12R rectangular and G12 square wafers. Incorporating the selective emitter (SE) technology, front silver (Ag) contacts with extensive area boron doping via laser, and backside microstructure reflector contacts, Trina Solar achieved a high-doping and low-resistance TOPCon structure, improving the cell efficiency to 26.2%. At the same time, the company reached 40 GW production capacity with the technology. The company is confident that its pure crystalline technology-based TOPCon technology, coupled with front-passivated contact cell technology, will push cell efficiency beyond 27%. Moreover, Trina Solar is optimistic about surpassing the 30% cell efficiency mark by making TOPCon the bottom cell in the next-generation tandem architectures. 

Reaching beyond 26%: Starting with 24.58% cell efficiency in 2019, Trina’s i-TOPCon technology breached the 26% efficiency threshold in 2023. (Photo Credit: TaiyangNews)

Switching wafer sizes to suit applications 

Trina Solar has developed a comprehensive i-TOPCon product portfolio based on the 210R and G12 wafer formats. The “Vertex S+” series, specifically designed for rooftop installations, utilizes the M12R (210 mm with rounded edges) wafer technology. These smaller, bifacial modules offer a power output of up to 450W and an efficiency of 22.5%. With dimensions of 1.762 x 1.1 m, resulting in an area of less than 2 m2, the module fits the requirements well for rooftop applications. 

Focusing on medium-sized products for utility-scale and C&I applications, Trina Solar is offering both p-type and n-type modules. The n-type “Vertex N NEG19RC.20″ series, based on the 210R wafer, delivers a maximum power output of 610 W and an efficiency of 22.5%. In contrast, the p-type “DEG19RC.20” series achieves a power output of 585 W with an efficiency of 21.7%. 

Chao Ye emphasized that the former is particularly effective in 1P tracker systems. It supports up to 3 strings and enables a maximum tracker length of 101 m. The improved open circuit voltage (Voc) of the M12R product results in a 13% higher power per tracker compared to the reference M10 products. These medium-sized modules are recognized for their “golden size” dimensions of 2382 x 1134 x 30 mm. Trina Solar’s flagship series for n-type modules, the NEG21C.20, boasts a power range of 710 W and an efficiency of 22.9%, whereas its p-type counterpart “DEG21C.20” series offers a power output of 675 W and an efficiency of 21.8%. These modules correspond to the so-called golden size dimensions of the larger modules category at 2384 x 1303 x 33 mm.

Still rectangular: Trina adopted the 210 mm size TOPCon cell for its larger modules to reach 710 W power output for utility applications. (Photo Credit: TaiyangNews)