Frontal metallization: efficiency accelerator

n-TOPCon SE creates more room for efficiency

Compared with the conventional p+ emitter, the p+ emitter SE process has a shallower junction in the non-metallized region, a deeper junction in the metallized region, and the surface concentration can be maintained at a reasonable level, which can significantly improve the emitter composite and metal composite, and also help to form a lower contact resistance. However, the laser SE process will cause certain damage to the suede structure, especially the pyramid spire, and the unoptimized silver aluminum paste may cause more serious damage to the corresponding site during the sintering process, which is not conducive to the improvement of metal composite. The metallization of p+ emitter SE should pay attention not only to the size and number control of the formed silver aluminum spikes, but also to the etching damage of the silver aluminum paste on the dielectric layer and the pyramid spire.

At the same time, the thin wire dense grid design will show a broader space for efficiency improvement on the n-TOPCon SE soalr cell. In 2023, silver aluminum paste is expected to achieve ultra-fine line printing of 10-13um screen plate opening, which further amplifies the importance of the midline resistance of the n-TOPCon soalr cell string resistance structure, and will become the key point of n-TOPCon silver aluminum paste inorganic and organic collaborative development. It is expected that n-TOPCon SE process optimization in conjunction with silver aluminum paste development and graphics optimization is expected to achieve a conversion efficiency gain of 0.3%-0.5%.

At present, the silver aluminum paste for the emitter SE process has become the benchmark metallization solution for the SE process development of most n-TOPCon solar cell customers through the collaborative innovation and integration optimization of the glass system and the silver/aluminum powder system.

Back metallization: cost booster

Four-quadrant, multi-dimensional to promote cost reduction

In the process of n-TOPCon soalr cell industrialization, the differentiated combination of front AlOx equipment and back PolySi equipment has an impact on the development and mass production of back silver paste in four quadrant dimensions such as back suede type and whether to introduce AlOx, and the differentiated equipment combination requires the back silver paste to have a very wide process window, compatible with alkali polishing/AlOx process. The backside silver paste provides customers with excellent performance and wide process window that has been widely proven in the market in the above four quadrants, and cooperates with customers to promote the development and mass production of ≤ 100nm PolySi process through customized development strategies to further improve efficiency and reduce costs.

At present, the opening and dosage of the silver paste screen plate on the back of the TOPCon soalr cell are higher than the silver aluminum paste on the front. In addition to improving metallization costs by advancing the back screen opening to within <15um through fine-line printing, combined with the specially developed glass system, silver powder combination, and organic carrier system, the low-solids backside silver paste is expected to significantly improve the cost of n-TOPCon sola cell backside metallization while maintaining cell conversion efficiency and EL yield.