The effect of matching glass frits on the metallization of n+ emitter by balancing wetting and sintering behavior

In the production of silicon solar cells, one of the key stages is the metallization process, where the softening temperature of the glass powder plays a decisive role in the metallization reaction. If the softening temperature is too low, it can lead to excessive erosion of the SiN_x layer. Conversely, if the softening temperature is too high, it may hinder the efficient completion of the metallization process. To address this issue, this study proposes an innovative concept that introduces a melting gradient in the glass binder phase of the electronic paste. Specifically, low-melting-point glass is tightly packed around high-melting-point glass. During the metallization process, the low-melting-point glass melts first, wetting and etching the substrate, while the high-melting-point glass etches the substrate more rapidly and facilitates the formation of silver crystals. The results demonstrate that the optimized mixed glass samples achieve a photovoltaic conversion efficiency improvement of 1.28–2.83% compared to pre-mixed and single glass melts. In particular, the M4 sample of the mixed glass exhibits the shortest melting process and the highest photovoltaic conversion efficiency (22.879%), along with the most significant recrystallization (0.057%). Transmission results indicate a large presence of silver nanoparticles in the glass layer, which can be attributed to the earlier melting of the low-temperature glass that erodes the SiN_x layer. This, in turn, allows the high-temperature glass to react with silver powder and silicon, resulting in the formation of abundant silver crystals. The key to this improvement lies in adjusting the glass's characteristic temperature, wettability, and etching properties, thereby enhancing the overall cell performance. This concept provides a novel approach to the design of conductive pastes, enabling independent tuning of interfacial reactions and thermal properties. It underscores the importance and remarkable performance of mixed glass materials with diverse properties, offering significant potential for various applications.